diff --git a/Src/Compilers/CSharp/Portable/CodeGen/EmitStatement.cs b/Src/Compilers/CSharp/Portable/CodeGen/EmitStatement.cs
index e7460dfad8efb6213875e1b12bd7458c34f6159f..ab72d141c71a96e777aea84240939740fa4accb3 100644
--- a/Src/Compilers/CSharp/Portable/CodeGen/EmitStatement.cs
+++ b/Src/Compilers/CSharp/Portable/CodeGen/EmitStatement.cs
@@ -759,7 +759,7 @@ private void EmitTryStatement(BoundTryStatement statement, bool emitCatchesOnly
         /// {
         ///    TryBlock
         /// }
-        /// catch (ExceptionType ex) if (Condition)
+        /// catch (ExceptionType ex) when (Condition)
         /// {
         ///    Handler
         /// }
diff --git a/Src/Compilers/CSharp/Portable/Parser/LanguageParser.cs b/Src/Compilers/CSharp/Portable/Parser/LanguageParser.cs
index bf64e356415979620a7e62f4750ef0a62122c68c..ce680817b7853b5943ca32377ee44323b4890c7f 100644
--- a/Src/Compilers/CSharp/Portable/Parser/LanguageParser.cs
+++ b/Src/Compilers/CSharp/Portable/Parser/LanguageParser.cs
@@ -7194,16 +7194,17 @@ private CatchClauseSyntax ParseCatchClause(bool hasCatchAll)
 
             CatchFilterClauseSyntax filter = null;
 
-            if (this.CurrentToken.Kind == SyntaxKind.IfKeyword)
+            if (this.CurrentToken.ContextualKind == SyntaxKind.WhenKeyword)
             {
-                var ifKeyword = CheckFeatureAvailability(this.EatToken(), MessageID.IDS_FeatureExceptionFilter);
+                var whenKeyword = this.EatContextualToken(SyntaxKind.WhenKeyword);
+                whenKeyword = CheckFeatureAvailability(whenKeyword, MessageID.IDS_FeatureExceptionFilter);
                 this.termState |= TerminatorState.IsEndOfilterClause;
                 var openParen = this.EatToken(SyntaxKind.OpenParenToken);
                 var filterExpression = this.ParseExpression();
 
                 this.termState = saveTerm;
                 var closeParen = this.EatToken(SyntaxKind.CloseParenToken);
-                filter = syntaxFactory.CatchFilterClause(ifKeyword, openParen, filterExpression, closeParen);
+                filter = syntaxFactory.CatchFilterClause(whenKeyword, openParen, filterExpression, closeParen);
             }
 
             this.termState |= TerminatorState.IsEndOfCatchBlock;
diff --git a/Src/Compilers/CSharp/Portable/Syntax/Syntax.xml b/Src/Compilers/CSharp/Portable/Syntax/Syntax.xml
index 54dba17e7cc3401199d3a51b461adcefbc574f0f..7c985544bf3d72ebd00df3e8bf9703031b6e478e 100644
--- a/Src/Compilers/CSharp/Portable/Syntax/Syntax.xml
+++ b/Src/Compilers/CSharp/Portable/Syntax/Syntax.xml
@@ -2108,8 +2108,8 @@
   </Node>
   <Node Name="CatchFilterClauseSyntax" Base="CSharpSyntaxNode">
     <Kind Name="CatchFilterClause"/>
-    <Field Name="IfKeyword" Type="SyntaxToken">
-      <Kind Name="IfKeyword"/>
+    <Field Name="WhenKeyword" Type="SyntaxToken">
+      <Kind Name="WhenKeyword"/>
     </Field>
     <Field Name="OpenParenToken" Type="SyntaxToken">
       <Kind Name="OpenParenToken"/>
diff --git a/Src/Compilers/CSharp/Portable/Syntax/SyntaxKind.cs b/Src/Compilers/CSharp/Portable/Syntax/SyntaxKind.cs
index 28233cc7e935bb1790b65d94befea6ed761ed99a..54dfb905e8d1bead09e2cc510ba9494ea7a7b3c5 100644
--- a/Src/Compilers/CSharp/Portable/Syntax/SyntaxKind.cs
+++ b/Src/Compilers/CSharp/Portable/Syntax/SyntaxKind.cs
@@ -191,6 +191,7 @@ public enum SyntaxKind : ushort
         NameOfKeyword = 8434,
         AsyncKeyword = 8435,
         AwaitKeyword = 8436,
+        WhenKeyword = 8437,
 
         // additional preprocessor keywords
         ElifKeyword = 8467,
diff --git a/Src/Compilers/CSharp/Portable/Syntax/SyntaxKindFacts.cs b/Src/Compilers/CSharp/Portable/Syntax/SyntaxKindFacts.cs
index 44350a0f00fbb21a0453088728763417995b33a2..b640ce8b7275e1dd41f300038293f1e076f9f6e6 100644
--- a/Src/Compilers/CSharp/Portable/Syntax/SyntaxKindFacts.cs
+++ b/Src/Compilers/CSharp/Portable/Syntax/SyntaxKindFacts.cs
@@ -1026,7 +1026,7 @@ public static SyntaxKind GetPreprocessorKeywordKind(string text)
 
         public static IEnumerable<SyntaxKind> GetContextualKeywordKinds()
         {
-            for (int i = (int)SyntaxKind.YieldKeyword; i <= (int)SyntaxKind.AwaitKeyword; i++)
+            for (int i = (int)SyntaxKind.YieldKeyword; i <= (int)SyntaxKind.WhenKeyword; i++)
             {
                 yield return (SyntaxKind)i;
             }
@@ -1068,6 +1068,7 @@ public static bool IsContextualKeyword(SyntaxKind kind)
                 case SyntaxKind.NameOfKeyword:
                 case SyntaxKind.AsyncKeyword:
                 case SyntaxKind.AwaitKeyword:
+                case SyntaxKind.WhenKeyword:
                     return true;
                 default:
                     return false;
@@ -1163,6 +1164,8 @@ public static SyntaxKind GetContextualKeywordKind(string text)
                     return SyntaxKind.AsyncKeyword;
                 case "await":
                     return SyntaxKind.AwaitKeyword;
+                case "when":
+                    return SyntaxKind.WhenKeyword;
                 case "nameof":
                     return SyntaxKind.NameOfKeyword;
                 default:
@@ -1556,6 +1559,8 @@ public static string GetText(SyntaxKind kind)
                     return "async";
                 case SyntaxKind.AwaitKeyword:
                     return "await";
+                case SyntaxKind.WhenKeyword:
+                    return "when";
                 case SyntaxKind.NameOfKeyword:
                     return "nameof";
                 default:
diff --git a/Src/Compilers/CSharp/Test/Emit/CodeGen/CodeGenAsyncEHTests.cs b/Src/Compilers/CSharp/Test/Emit/CodeGen/CodeGenAsyncEHTests.cs
index ec40485e8dea9bcefebb8e2cec91b37ac8a74b06..163d7c9d5fde087854f5832780330f905eb484fe 100644
--- a/Src/Compilers/CSharp/Test/Emit/CodeGen/CodeGenAsyncEHTests.cs
+++ b/Src/Compilers/CSharp/Test/Emit/CodeGen/CodeGenAsyncEHTests.cs
@@ -1235,13 +1235,13 @@ static async Task<int> G()
             {
                 x = x / x;
             }
-            catch if(x != 0)
+            catch when(x != 0)
             {
                 x = await F();
                 throw;
             }
         }
-        catch(Exception ex) if(x == 0 && ((ex = new Exception(""hello"")) != null))
+        catch(Exception ex) when(x == 0 && ((ex = new Exception(""hello"")) != null))
         {
             x = await F();
             System.Console.WriteLine(ex.Message);
@@ -1294,12 +1294,12 @@ static async Task<int> G()
         {
             x = x / x;
         }
-        catch(Exception ex) if(T(()=>ex.Message == null, ref ex))
+        catch(Exception ex) when(T(()=>ex.Message == null, ref ex))
         {
             x = await F();
             System.Console.WriteLine(ex.Message);
         }
-        catch(Exception ex) if(T(()=>ex.Message != null, ref ex))
+        catch(Exception ex) when(T(()=>ex.Message != null, ref ex))
         {
             x = await F();
             System.Console.WriteLine(ex.Message);
@@ -1351,7 +1351,7 @@ static async Task<int> G()
                         {
                             x = x / await F(0);
                         }
-                        catch (DivideByZeroException) if (i < 3)
+                        catch (DivideByZeroException) when (i < 3)
                         {
                             await Task.Yield();
                             continue;
@@ -1434,7 +1434,7 @@ static Func<Task<int>> G()
                             {
                                 x = x / await F(0);
                             }
-                            catch (DivideByZeroException) if (i < 3)
+                            catch (DivideByZeroException) when (i < 3)
                             {
                                 await Task.Yield();
                                 continue;
diff --git a/Src/Compilers/CSharp/Test/Emit/CodeGen/CodeGenClosureLambdaTests.cs b/Src/Compilers/CSharp/Test/Emit/CodeGen/CodeGenClosureLambdaTests.cs
index d9818cc20498d367fc035ac6fd942b352586520e..7ef4225eca8528b7407e805a05c8ae8f9a562969 100644
--- a/Src/Compilers/CSharp/Test/Emit/CodeGen/CodeGenClosureLambdaTests.cs
+++ b/Src/Compilers/CSharp/Test/Emit/CodeGen/CodeGenClosureLambdaTests.cs
@@ -640,7 +640,7 @@ static void Main()
         {
             throw new Exception(""xxx"");
         }
-        catch (Exception e) if (new Func<Exception, bool>(x => x.Message == s)(e))
+        catch (Exception e) when (new Func<Exception, bool>(x => x.Message == s)(e))
         {
             Console.Write(""pass"");
         }
@@ -664,7 +664,7 @@ static void Main()
         {
             throw new Exception(""xxx"");
         }
-        catch (Exception e) if (new Func<Exception, bool>(x => x.Message == s)(e))
+        catch (Exception e) when (new Func<Exception, bool>(x => x.Message == s)(e))
         {
             Console.Write(s + ""pass"");
         }
@@ -752,7 +752,7 @@ static void Main()
         {
             throw new Exception(""fail"");
         }
-        catch (Exception ex) if (Foo(() => { ex = new Exception(""pass""); }))
+        catch (Exception ex) when (Foo(() => { ex = new Exception(""pass""); }))
         {
             Console.Write(ex.Message);
         }
@@ -828,11 +828,11 @@ static void Main()
         {
             throw new Exception(""fail"");
         }
-        catch (ArgumentException ex) if (Foo(() => { ex = new ArgumentException(""fail""); }))
+        catch (ArgumentException ex) when (Foo(() => { ex = new ArgumentException(""fail""); }))
         {
             Console.Write(ex.Message);
         }
-        catch (Exception ex) if (Foo(() => { ex = new Exception(""pass""); }))
+        catch (Exception ex) when (Foo(() => { ex = new Exception(""pass""); }))
         {
             Console.Write(ex.Message);
         }
@@ -855,7 +855,7 @@ static void Main()
         {
             throw new Exception(""xxx"");
         }
-        catch (Exception e) if (new Func<bool>(() => e.Message == ""xxx"")())
+        catch (Exception e) when (new Func<bool>(() => e.Message == ""xxx"")())
         {
             Console.Write(""pass"");
         }
@@ -929,7 +929,7 @@ static void Main()
             {
                 throw new IOException(""xxx"");
             }
-            catch (T e) if (e.Message == ""xxx"")
+            catch (T e) when (e.Message == ""xxx"")
             {
                 Console.Write(""pass"");
             }
@@ -1001,7 +1001,7 @@ static void Main()
             {
                 throw new IOException(""xy"");
             }
-            catch (T e) if (new Func<bool>(() => e.Message == x + y)())
+            catch (T e) when (new Func<bool>(() => e.Message == x + y)())
             {
                 Console.Write(""pass_"" + x + y);
             }
@@ -1099,7 +1099,7 @@ static void Main()
             {
                 throw new IOException(""a"");
             }
-            catch (T e1) if (new Func<bool>(() => 
+            catch (T e1) when (new Func<bool>(() => 
                 {
                     string z = ""z"";
 
@@ -1107,7 +1107,7 @@ static void Main()
                     {
                         throw new IOException(""xyz"");
                     }
-                    catch (T e2) if (e2.Message == x + y + z)
+                    catch (T e2) when (e2.Message == x + y + z)
                     {
                         return true;
                     }
diff --git a/Src/Compilers/CSharp/Test/Emit/CodeGen/CodeGenTryFinally.cs b/Src/Compilers/CSharp/Test/Emit/CodeGen/CodeGenTryFinally.cs
index 6dfccf06fe27dd67f61edba514ed6b5ab0956712..44ed5de7fe33c83b01683c1c6515dfa5cbee6d30 100644
--- a/Src/Compilers/CSharp/Test/Emit/CodeGen/CodeGenTryFinally.cs
+++ b/Src/Compilers/CSharp/Test/Emit/CodeGen/CodeGenTryFinally.cs
@@ -454,7 +454,7 @@ static void Main()
         {
             throw new Exception(""hello"");
         }
-        catch (Exception ex1) if (ex1.Message == null)
+        catch (Exception ex1) when (ex1.Message == null)
         {
         }
 
@@ -462,7 +462,7 @@ static void Main()
         {
             throw new Exception(""bye"");
         }
-        catch (Exception ex2) if (F(ex2, ex2))
+        catch (Exception ex2) when (F(ex2, ex2))
         {
         }
     }
@@ -548,7 +548,7 @@ static void Main()
         {
             throw new Exception(""bye"");
         }
-        catch (Exception ex) if (F(ex, ex))
+        catch (Exception ex) when (F(ex, ex))
         {
             Console.WriteLine(ex);
         }
@@ -614,7 +614,7 @@ static void Main()
         {
             throw new Exception(""bye"");
         }
-        catch (Exception ex) if (F(ref ex))
+        catch (Exception ex) when (F(ref ex))
         {
             Console.WriteLine(ex);
         }
@@ -679,7 +679,7 @@ class Program
         {
             throw new Exception(""bye"");
         }
-        catch (T ex) if (F(ex, ex))
+        catch (T ex) when (F(ex, ex))
         {
             Console.WriteLine(ex);
         }
@@ -779,7 +779,7 @@ class C
 		{
 			throw new IOException(""Hi"");
         }
-		catch (E e) if (new Func<bool>(() => e.Message != null)())
+		catch (E e) when (new Func<bool>(() => e.Message != null)())
 		{
 			( (Action) delegate { Console.WriteLine(e.Message); })();
 		}
@@ -1421,7 +1421,7 @@ static void Main()
             Console.Write(""Try"");
             x = x / x;
         }
-        catch if (Filter())
+        catch when (Filter())
         {
             Console.Write(""Catch"");
         }
@@ -1500,12 +1500,12 @@ static void Main()
             x = x / x;
         }
         catch (DivideByZeroException e)
-              if (e.Message == null)
+              when (e.Message == null)
         {
             Console.Write(""Catch1"");
         }
         catch (DivideByZeroException e)
-               if(e.Message != null)
+               when (e.Message != null)
         {
             Console.Write(""Catch2"" + e.Message.Length);
         }
@@ -1615,7 +1615,7 @@ static void Main()
             Console.Write(""Try"");
             x = x / x;
         }
-        catch if (new Func<bool>(() => str.Length == 2)())
+        catch when (new Func<bool>(() => str.Length == 2)())
         {
             Console.Write(""Catch"" + str);
         }
@@ -1939,13 +1939,13 @@ static void M()
         int a = 1;
         try { }
         catch (System.Exception) { }
-        catch if (a == 1) { }
+        catch when (a == 1) { }
     }
 }
 ";
             CreateCompilationWithMscorlib(text).VerifyDiagnostics(
                 // (9,9): warning CS1058: A previous catch clause already catches all exceptions. All non-exceptions thrown will be wrapped in a System.Runtime.CompilerServices.RuntimeWrappedException.
-                //         catch if (a == 1) { }
+                //         catch when (a == 1) { }
                 Diagnostic(ErrorCode.WRN_UnreachableGeneralCatch, "catch").WithLocation(9, 9));
         }
 
@@ -1959,8 +1959,8 @@ static void M()
     {
         int a = 1;
         try { }
-        catch if (a == 2) { }
-        catch (System.Exception) if (a == 3) { }
+        catch when (a == 2) { }
+        catch (System.Exception) when (a == 3) { }
         catch { }
     }
 }
diff --git a/Src/Compilers/CSharp/Test/Emit/Emit/EditAndContinue/EditAndContinueTests.cs b/Src/Compilers/CSharp/Test/Emit/Emit/EditAndContinue/EditAndContinueTests.cs
index 059079b8504067e5e8015fce94d3e38767a5cc02..4364f5dabc73dbcff1a85185a2ae1933326737c2 100644
--- a/Src/Compilers/CSharp/Test/Emit/Emit/EditAndContinue/EditAndContinueTests.cs
+++ b/Src/Compilers/CSharp/Test/Emit/Emit/EditAndContinue/EditAndContinueTests.cs
@@ -4762,7 +4762,7 @@ .maxstack  3
         }
 
         /// Local names array (from PDB) may have fewer slots than method
-        /// signature (from metadata) if the trailing slots are unnamed.
+        /// signature (from metadata) when the trailing slots are unnamed.
         /// </summary>
         [WorkItem(782270, "DevDiv")]
         [Fact]
diff --git a/Src/Compilers/CSharp/Test/Emit/PDB/PDBTests.cs b/Src/Compilers/CSharp/Test/Emit/PDB/PDBTests.cs
index b89c2c0b3b82e3c8cd0ee7b247017c5007cef124..f063bfe0611e4533c4a4d0aecb6e995af979c1b0 100644
--- a/Src/Compilers/CSharp/Test/Emit/PDB/PDBTests.cs
+++ b/Src/Compilers/CSharp/Test/Emit/PDB/PDBTests.cs
@@ -2611,7 +2611,7 @@ static void Main()
         {
             throw new System.Exception();
         }
-        catch (System.Exception e) if (e.Message != null)
+        catch (System.Exception e) when (e.Message != null)
         { 
             System.Console.WriteLine();
         }
@@ -2636,7 +2636,7 @@ static void Main()
         <entry il_offset=""0x1"" start_row=""7"" start_column=""9"" end_row=""7"" end_column=""10"" file_ref=""0"" />
         <entry il_offset=""0x2"" start_row=""8"" start_column=""13"" end_row=""8"" end_column=""42"" file_ref=""0"" />
         <entry il_offset=""0x8"" hidden=""true"" start_row=""16707566"" start_column=""0"" end_row=""16707566"" end_column=""0"" file_ref=""0"" />
-        <entry il_offset=""0x15"" start_row=""10"" start_column=""36"" end_row=""10"" end_column=""58"" file_ref=""0"" />
+        <entry il_offset=""0x15"" start_row=""10"" start_column=""36"" end_row=""10"" end_column=""60"" file_ref=""0"" />
         <entry il_offset=""0x23"" hidden=""true"" start_row=""16707566"" start_column=""0"" end_row=""16707566"" end_column=""0"" file_ref=""0"" />
         <entry il_offset=""0x24"" start_row=""11"" start_column=""9"" end_row=""11"" end_column=""10"" file_ref=""0"" />
         <entry il_offset=""0x25"" start_row=""12"" start_column=""13"" end_row=""12"" end_column=""40"" file_ref=""0"" />
@@ -2653,8 +2653,7 @@ static void Main()
       </scope>
     </method>
   </methods>
-</symbols>
-");
+</symbols>");
         }
 
         [Fact]
@@ -2669,7 +2668,7 @@ static void Main()
         {
             throw new System.Exception();
         }
-        catch if (F())
+        catch when (F())
         { 
             System.Console.WriteLine();
         }
@@ -2696,7 +2695,7 @@ private static bool F()
         <entry il_offset=""0x1"" start_row=""7"" start_column=""9"" end_row=""7"" end_column=""10"" file_ref=""0"" />
         <entry il_offset=""0x2"" start_row=""8"" start_column=""13"" end_row=""8"" end_column=""42"" file_ref=""0"" />
         <entry il_offset=""0x8"" hidden=""true"" start_row=""16707566"" start_column=""0"" end_row=""16707566"" end_column=""0"" file_ref=""0"" />
-        <entry il_offset=""0x15"" start_row=""10"" start_column=""15"" end_row=""10"" end_column=""23"" file_ref=""0"" />
+        <entry il_offset=""0x15"" start_row=""10"" start_column=""15"" end_row=""10"" end_column=""25"" file_ref=""0"" />
         <entry il_offset=""0x1f"" hidden=""true"" start_row=""16707566"" start_column=""0"" end_row=""16707566"" end_column=""0"" file_ref=""0"" />
         <entry il_offset=""0x20"" start_row=""11"" start_column=""9"" end_row=""11"" end_column=""10"" file_ref=""0"" />
         <entry il_offset=""0x21"" start_row=""12"" start_column=""13"" end_row=""12"" end_column=""40"" file_ref=""0"" />
@@ -2706,8 +2705,7 @@ private static bool F()
       <locals />
     </method>
   </methods>
-</symbols>
-");
+</symbols>");
         }
 
         [WorkItem(778655, "DevDiv")]
diff --git a/Src/Compilers/CSharp/Test/Semantic/FlowAnalysis/FlowTests.cs b/Src/Compilers/CSharp/Test/Semantic/FlowAnalysis/FlowTests.cs
index a30cd283c43f987898fc7d8a65971b2fd6aee2a2..667488224c94274ecaa42a11ea1dcb07a226b179 100644
--- a/Src/Compilers/CSharp/Test/Semantic/FlowAnalysis/FlowTests.cs
+++ b/Src/Compilers/CSharp/Test/Semantic/FlowAnalysis/FlowTests.cs
@@ -2066,7 +2066,7 @@ static void Main()
         try
         {
         }
-        catch (System.Exception e) if (e.Message == null)
+        catch (System.Exception e) when (e.Message == null)
         {
         }
     }
@@ -2086,7 +2086,7 @@ static void Main()
         try
         {
         }
-        catch (System.Exception e) if (F())
+        catch (System.Exception e) when (F())
         {
         }
     }
@@ -2096,7 +2096,7 @@ static void Main()
 ";
             CreateCompilationWithMscorlib(source).VerifyDiagnostics(
                 // (9,33): warning CS0168: The variable 'e' is declared but never used
-                //         catch (System.Exception e) if (true)
+                //         catch (System.Exception e) when (true)
                 Diagnostic(ErrorCode.WRN_UnreferencedVar, "e").WithArguments("e").WithLocation(9, 33));
         }
 
@@ -2114,7 +2114,7 @@ static void Main()
         try
         {
         }
-        catch (Exception e) if ((f = e) != null)
+        catch (Exception e) when ((f = e) != null)
         {
             Console.WriteLine(f);
         }
@@ -2138,7 +2138,7 @@ static void Main()
         try
         {
         }
-        catch (Exception e) if (f == e)
+        catch (Exception e) when (f == e)
         {
         }
     }
@@ -2146,7 +2146,7 @@ static void Main()
 ";
             CreateCompilationWithMscorlib(source).VerifyDiagnostics(
                 // (12,33): error CS0165: Use of unassigned local variable 'f'
-                //         catch (Exception e) if (f == e)
+                //         catch (Exception e) when (f == e)
                 Diagnostic(ErrorCode.ERR_UseDefViolation, "f").WithArguments("f"));
         }
 
@@ -2164,10 +2164,10 @@ static void Main()
         try
         {
         }
-        catch (Exception e) if ((f = e) != null)
+        catch (Exception e) when ((f = e) != null)
         {
         }
-        catch (Exception e) if (f == e)
+        catch (Exception e) when (f == e)
         {
         }
     }
@@ -2176,7 +2176,7 @@ static void Main()
             // TODO (tomat): f is always gonna be assigned in subsequent filter expressions.
             CreateCompilationWithMscorlib(source).VerifyDiagnostics(
                 // (15,33): error CS0165: Use of unassigned local variable 'f'
-                //         catch (Exception e) if (f == e)
+                //         catch (Exception e) when (f == e)
                 Diagnostic(ErrorCode.ERR_UseDefViolation, "f").WithArguments("f"));
         }
 
@@ -2194,7 +2194,7 @@ static void Main()
         try
         {
         }
-        catch (Exception e) if ((f = e) != null)
+        catch (Exception e) when ((f = e) != null)
         {
             Console.WriteLine(f);
             Console.WriteLine(g);
diff --git a/Src/Compilers/CSharp/Test/Semantic/Semantics/BindingAsyncTests.cs b/Src/Compilers/CSharp/Test/Semantic/Semantics/BindingAsyncTests.cs
index e4bacbfea6f5f17e0e7fcb55821489f4d7f148ef..293fba1443cda33711174b02a6ee6a08060f16e4 100644
--- a/Src/Compilers/CSharp/Test/Semantic/Semantics/BindingAsyncTests.cs
+++ b/Src/Compilers/CSharp/Test/Semantic/Semantics/BindingAsyncTests.cs
@@ -931,7 +931,7 @@ async static Task M1()
         try
         {
         }
-        catch if (await Task.Factory.StartNew(() => false))
+        catch when (await Task.Factory.StartNew(() => false))
         {
         }
         finally
@@ -941,8 +941,8 @@ async static Task M1()
 }";
             CreateCompilationWithMscorlib45(source).VerifyDiagnostics(
                 // (11,19): error CS7094: Cannot await in the filter expression of a catch clause
-                //         catch if (await Task.Factory.StartNew(() => false))
-                Diagnostic(ErrorCode.ERR_BadAwaitInCatchFilter, "await Task.Factory.StartNew(() => false)").WithLocation(11, 19)
+                //         catch when (await Task.Factory.StartNew(() => false))
+                Diagnostic(ErrorCode.ERR_BadAwaitInCatchFilter, "await Task.Factory.StartNew(() => false)").WithLocation(11, 21)
                 );
         }
 
diff --git a/Src/Compilers/CSharp/Test/Semantic/Semantics/DynamicTests.cs b/Src/Compilers/CSharp/Test/Semantic/Semantics/DynamicTests.cs
index 5f3a788e8a178a1ab3995669e42c0937371c420d..d49aa3047adecff5c5ec901e3e6c461e79da8ded 100644
--- a/Src/Compilers/CSharp/Test/Semantic/Semantics/DynamicTests.cs
+++ b/Src/Compilers/CSharp/Test/Semantic/Semantics/DynamicTests.cs
@@ -3184,7 +3184,7 @@ void M()
         try
         {
         }
-        catch (Exception e) if (d)  //-local: System.Exception
+        catch (Exception e) when (d)  //-local: System.Exception
                                     //-thisReference: C
                                     //-fieldAccess: dynamic
                                     //-unaryOperator: bool
diff --git a/Src/Compilers/CSharp/Test/Semantic/Semantics/SemanticErrorTests.cs b/Src/Compilers/CSharp/Test/Semantic/Semantics/SemanticErrorTests.cs
index 25108b20cdf648995b12bc5510b92d3e9c675bf4..ceb177753e26aff89e76c80effb9f793792b7157 100644
--- a/Src/Compilers/CSharp/Test/Semantic/Semantics/SemanticErrorTests.cs
+++ b/Src/Compilers/CSharp/Test/Semantic/Semantics/SemanticErrorTests.cs
@@ -5143,16 +5143,16 @@ static void M()
     {
         int a = 1;
         try { }
-        catch if (a == 1) { }
-        catch (Exception e) if (e.Message == null) { }
+        catch when (a == 1) { }
+        catch (Exception e) when (e.Message == null) { }
         catch (A) { }
-        catch (B e) if (e.Message == null) { }
+        catch (B e) when (e.Message == null) { }
     }
 }
 ";
             CreateCompilationWithMscorlib(text).VerifyDiagnostics(
                 // (15,16): error CS0160: A previous catch clause already catches all exceptions of this or of a super type ('A')
-                //         catch (B e) if (e.Message == null) { }
+                //         catch (B e) when (e.Message == null) { }
                 Diagnostic(ErrorCode.ERR_UnreachableCatch, "B").WithArguments("A").WithLocation(15, 16));
         }
 
@@ -5169,15 +5169,15 @@ class Program
     static void M()
     {
         try { }
-        catch (A) if (true) { }
+        catch (A) when (true) { }
         catch (B) { }
     }
 }
 ";
             CreateCompilationWithMscorlib(text).VerifyDiagnostics(
                 // (11,23): warning CS7095: Filter expression is a constant, consider removing the filter
-                //         catch (A) if (true) { }
-                Diagnostic(ErrorCode.WRN_FilterIsConstant, "true").WithLocation(11, 23));
+                //         catch (A) when (true) { }
+                Diagnostic(ErrorCode.WRN_FilterIsConstant, "true").WithLocation(11, 25));
         }
 
         [Fact]
@@ -5192,19 +5192,19 @@ class Program
     static void M()
     {
         try { }
-        catch if (true) { }
+        catch when (true) { }
         catch (A) { }
-        catch if (false) { }
+        catch when (false) { }
     }
 }
 ";
             CreateCompilationWithMscorlib(text).VerifyDiagnostics(
                 // (10,19): warning CS7095: Filter expression is a constant, consider removing the filter
-                //         catch if (true) { }
-                Diagnostic(ErrorCode.WRN_FilterIsConstant, "true").WithLocation(10, 19),
+                //         catch when (true) { }
+                Diagnostic(ErrorCode.WRN_FilterIsConstant, "true").WithLocation(10, 21),
                 // (12,19): warning CS7095: Filter expression is a constant, consider removing the filter
-                //         catch if (false) { }
-                Diagnostic(ErrorCode.WRN_FilterIsConstant, "false").WithLocation(12, 19));
+                //         catch when (false) { }
+                Diagnostic(ErrorCode.WRN_FilterIsConstant, "false").WithLocation(12, 21));
         }
 
         [Fact]
@@ -5220,7 +5220,7 @@ class Program
     static void M()
     {
         try { }
-        catch (A) if (false) 
+        catch (A) when (false) 
         {
             Console.WriteLine(1); 
         }
@@ -5229,9 +5229,10 @@ static void M()
 }
 ";
             CreateCompilationWithMscorlib(text).VerifyDiagnostics(
-                // (11,23): warning CS7095: Filter expression is a constant, consider removing the filter
-                //         catch (A) if (false) 
-                Diagnostic(ErrorCode.WRN_FilterIsConstant, "false").WithLocation(11, 23));
+    // (11,25): warning CS7095: Filter expression is a constant, consider removing the filter
+    //         catch (A) when (false) 
+    Diagnostic(ErrorCode.WRN_FilterIsConstant, "false").WithLocation(11, 25)
+                );
         }
 
         [Fact]
@@ -5246,7 +5247,7 @@ static void M()
     {
         int x;
         try { }
-        catch (Exception) if (false) 
+        catch (Exception) when (false) 
         {
             Console.WriteLine(x);
         }
@@ -5258,12 +5259,13 @@ static void M()
             // is to make conditional compilation easier. Such scenario doesn't apply to filters.
 
             CreateCompilationWithMscorlib(text).VerifyDiagnostics(
-                // (10,31): warning CS7095: Filter expression is a constant, consider removing the filter
-                //         catch (Exception) if (false) 
-                Diagnostic(ErrorCode.WRN_FilterIsConstant, "false").WithLocation(10, 31),
-                // (12,31): error CS0165: Use of unassigned local variable 'x'
-                //             Console.WriteLine(x);
-                Diagnostic(ErrorCode.ERR_UseDefViolation, "x").WithArguments("x").WithLocation(12, 31));
+    // (10,33): warning CS7095: Filter expression is a constant, consider removing the filter
+    //         catch (Exception) when (false) 
+    Diagnostic(ErrorCode.WRN_FilterIsConstant, "false").WithLocation(10, 33),
+    // (12,31): error CS0165: Use of unassigned local variable 'x'
+    //             Console.WriteLine(x);
+    Diagnostic(ErrorCode.ERR_UseDefViolation, "x").WithArguments("x").WithLocation(12, 31)
+                );
         }
 
         [Fact]
diff --git a/Src/Compilers/CSharp/Test/Semantic/Semantics/TryCatchTests.cs b/Src/Compilers/CSharp/Test/Semantic/Semantics/TryCatchTests.cs
index 32a6ac5d680923a37c6e05c0cd082c475cd8f426..931fcb8be514b9c9c8016989e835fdbd6ae6d6db 100644
--- a/Src/Compilers/CSharp/Test/Semantic/Semantics/TryCatchTests.cs
+++ b/Src/Compilers/CSharp/Test/Semantic/Semantics/TryCatchTests.cs
@@ -25,7 +25,7 @@ static void Main()
         try
         {
         }
-        catch (System.IO.IOException e) if (e.Message != null)
+        catch (System.IO.IOException e) when (e.Message != null)
         {
         }
     }
diff --git a/Src/Compilers/CSharp/Test/Syntax/Parsing/ParserErrorMessageTests.cs b/Src/Compilers/CSharp/Test/Syntax/Parsing/ParserErrorMessageTests.cs
index 202045d333a2e39abbfa7cc6869afe88eddac5e9..8d3a8b0fd26b5cb4486dbff1b8abb1e44cc19bd2 100644
--- a/Src/Compilers/CSharp/Test/Syntax/Parsing/ParserErrorMessageTests.cs
+++ b/Src/Compilers/CSharp/Test/Syntax/Parsing/ParserErrorMessageTests.cs
@@ -1689,7 +1689,7 @@ public static int Main()
         catch {}
         catch (S1) {}
         catch (S) {}
-        catch if (false) {}
+        catch when (false) {}
         if (retval == 0) Console.WriteLine(""PASS"");
         else Console.WriteLine(""FAIL"");
            return retval;
@@ -1721,7 +1721,7 @@ public static int Main()
         try {
                 throw new S();
         }
-        catch if (true) {}
+        catch when (true) {}
         catch (S1) {}
         catch (S) {}
         if (retval == 0) Console.WriteLine(""PASS"");
@@ -4240,7 +4240,7 @@ public class C
 {
     public static int Main()
     {
-        try { } catch if (true) {}
+        try { } catch when (true) {}
     }
 }
 ";
@@ -4249,9 +4249,10 @@ public static int Main()
 
             tree = Parse(text, options: CSharpParseOptions.Default.WithLanguageVersion(LanguageVersion.CSharp5));
             tree.GetDiagnostics().Verify(
-                // (6,23): error CS8026: Feature 'exception filter' is not available in C# 5.  Please use language version 6 or greater.
-                //         try { } catch if (true) {}
-                Diagnostic(ErrorCode.ERR_FeatureNotAvailableInVersion5, "if").WithArguments("exception filter", "6"));
+    // (6,23): error CS8026: Feature 'exception filter' is not available in C# 5.  Please use language version 6 or greater.
+    //         try { } catch when (true) {}
+    Diagnostic(ErrorCode.ERR_FeatureNotAvailableInVersion5, "when").WithArguments("exception filter", "6").WithLocation(6, 23)
+                );
         }
 
         #endregion
@@ -4678,7 +4679,7 @@ public void CSharp6Features()
     void P(object o)
     {
         try {
-        } catch (Exception ex) if (ex.ToString() == null) { // exception filter
+        } catch (Exception ex) when (ex.ToString() == null) { // exception filter
         }
 
         var s = o?.ToString(); // null propagating operator
@@ -4687,30 +4688,31 @@ void P(object o)
             SyntaxFactory.ParseSyntaxTree(source, options: CSharpParseOptions.Default.WithLanguageVersion(LanguageVersion.CSharp6)).GetDiagnostics().Verify();
 
             SyntaxFactory.ParseSyntaxTree(source, options: CSharpParseOptions.Default.WithLanguageVersion(LanguageVersion.CSharp5)).GetDiagnostics().Verify(
-                // (3,20): error CS8026: Feature 'auto property initializer' is not available in C# 5.  Please use language version 6 or greater.
-                //     int L { get; } = 12; // auto property initializer
-                Diagnostic(ErrorCode.ERR_FeatureNotAvailableInVersion5, "= 12").WithArguments("auto property initializer", "6").WithLocation(3, 20),
-                // (5,13): error CS8026: Feature 'expression-bodied method' is not available in C# 5.  Please use language version 6 or greater.
-                //     int M() => 12; // expression-bodied method
-                Diagnostic(ErrorCode.ERR_FeatureNotAvailableInVersion5, "=> 12").WithArguments("expression-bodied method", "6").WithLocation(5, 13),
-                // (7,11): error CS8026: Feature 'expression-bodied property' is not available in C# 5.  Please use language version 6 or greater.
-                //     int N => 12; // expression-bodied property
-                Diagnostic(ErrorCode.ERR_FeatureNotAvailableInVersion5, "=> 12").WithArguments("expression-bodied property", "6").WithLocation(7, 11),
-                // (9,21): error CS8026: Feature 'expression-bodied indexer' is not available in C# 5.  Please use language version 6 or greater.
-                //     int this[int a] => a + 1; // expression-bodied indexer
-                Diagnostic(ErrorCode.ERR_FeatureNotAvailableInVersion5, "=> a + 1").WithArguments("expression-bodied indexer", "6").WithLocation(9, 21),
-                // (11,48): error CS8026: Feature 'expression-bodied method' is not available in C# 5.  Please use language version 6 or greater.
-                //     public static int operator +(Foo a, Foo b) => null; // expression-bodied operator
-                Diagnostic(ErrorCode.ERR_FeatureNotAvailableInVersion5, "=> null").WithArguments("expression-bodied method", "6").WithLocation(11, 48),
-                // (13,49): error CS8026: Feature 'expression-bodied method' is not available in C# 5.  Please use language version 6 or greater.
-                //     public static explicit operator bool(Foo a) => false; // expression-bodied conversion operator
-                Diagnostic(ErrorCode.ERR_FeatureNotAvailableInVersion5, "=> false").WithArguments("expression-bodied method", "6").WithLocation(13, 49),
-                // (18,32): error CS8026: Feature 'exception filter' is not available in C# 5.  Please use language version 6 or greater.
-                //         } catch (Exception ex) if (ex.ToString() == null) { // exception filter
-                Diagnostic(ErrorCode.ERR_FeatureNotAvailableInVersion5, "if").WithArguments("exception filter", "6").WithLocation(18, 32),
-                // (21,17): error CS8026: Feature 'null propagating operator' is not available in C# 5.  Please use language version 6 or greater.
-                //         var s = o?.ToString(); // null propagating operator
-                Diagnostic(ErrorCode.ERR_FeatureNotAvailableInVersion5, "o?.ToString()").WithArguments("null propagating operator", "6").WithLocation(21, 17));
+    // (3,20): error CS8026: Feature 'auto property initializer' is not available in C# 5.  Please use language version 6 or greater.
+    //     int L { get; } = 12; // auto property initializer
+    Diagnostic(ErrorCode.ERR_FeatureNotAvailableInVersion5, "= 12").WithArguments("auto property initializer", "6").WithLocation(3, 20),
+    // (5,13): error CS8026: Feature 'expression-bodied method' is not available in C# 5.  Please use language version 6 or greater.
+    //     int M() => 12; // expression-bodied method
+    Diagnostic(ErrorCode.ERR_FeatureNotAvailableInVersion5, "=> 12").WithArguments("expression-bodied method", "6").WithLocation(5, 13),
+    // (7,11): error CS8026: Feature 'expression-bodied property' is not available in C# 5.  Please use language version 6 or greater.
+    //     int N => 12; // expression-bodied property
+    Diagnostic(ErrorCode.ERR_FeatureNotAvailableInVersion5, "=> 12").WithArguments("expression-bodied property", "6").WithLocation(7, 11),
+    // (9,21): error CS8026: Feature 'expression-bodied indexer' is not available in C# 5.  Please use language version 6 or greater.
+    //     int this[int a] => a + 1; // expression-bodied indexer
+    Diagnostic(ErrorCode.ERR_FeatureNotAvailableInVersion5, "=> a + 1").WithArguments("expression-bodied indexer", "6").WithLocation(9, 21),
+    // (11,48): error CS8026: Feature 'expression-bodied method' is not available in C# 5.  Please use language version 6 or greater.
+    //     public static int operator +(Foo a, Foo b) => null; // expression-bodied operator
+    Diagnostic(ErrorCode.ERR_FeatureNotAvailableInVersion5, "=> null").WithArguments("expression-bodied method", "6").WithLocation(11, 48),
+    // (13,49): error CS8026: Feature 'expression-bodied method' is not available in C# 5.  Please use language version 6 or greater.
+    //     public static explicit operator bool(Foo a) => false; // expression-bodied conversion operator
+    Diagnostic(ErrorCode.ERR_FeatureNotAvailableInVersion5, "=> false").WithArguments("expression-bodied method", "6").WithLocation(13, 49),
+    // (18,32): error CS8026: Feature 'exception filter' is not available in C# 5.  Please use language version 6 or greater.
+    //         } catch (Exception ex) when (ex.ToString() == null) { // exception filter
+    Diagnostic(ErrorCode.ERR_FeatureNotAvailableInVersion5, "when").WithArguments("exception filter", "6").WithLocation(18, 32),
+    // (21,17): error CS8026: Feature 'null propagating operator' is not available in C# 5.  Please use language version 6 or greater.
+    //         var s = o?.ToString(); // null propagating operator
+    Diagnostic(ErrorCode.ERR_FeatureNotAvailableInVersion5, "o?.ToString()").WithArguments("null propagating operator", "6").WithLocation(21, 17)
+                );
         }
 
         [Fact]