diff --git a/src/fsharp/FSharp.Compiler.Unittests/FSharp.Compiler.Unittests.fsproj b/src/fsharp/FSharp.Compiler.Unittests/FSharp.Compiler.Unittests.fsproj
index 280b96abace23d247e55c40c68dd2d241cc5732c..5a38e3aa85f5ab00e9a713dcbc9d630fc938ed99 100644
--- a/src/fsharp/FSharp.Compiler.Unittests/FSharp.Compiler.Unittests.fsproj
+++ b/src/fsharp/FSharp.Compiler.Unittests/FSharp.Compiler.Unittests.fsproj
@@ -1,4 +1,4 @@
-<?xml version="1.0" encoding="utf-8"?>
+<?xml version="1.0" encoding="utf-8"?>
 <!-- Copyright (c) Microsoft Open Technologies, Inc.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information. -->
 <Project ToolsVersion="4.0" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   <PropertyGroup>
@@ -60,6 +60,7 @@
   </ItemGroup>
   <ItemGroup>
     <Compile Include="NUnitFrameworkShims.fs" Condition="'$(TargetFramework)' == 'sl3-wp'" />
+    <Compile Include="ManglingNameOfProvidedTypes.fs" />
     <Compile Include="HashIfExpression.fs" />
   </ItemGroup>
   <ItemGroup>
diff --git a/src/fsharp/FSharp.Compiler.Unittests/ManglingNameOfProvidedTypes.fs b/src/fsharp/FSharp.Compiler.Unittests/ManglingNameOfProvidedTypes.fs
new file mode 100644
index 0000000000000000000000000000000000000000..0180e6abdd284827997884a9daded11e2d8127d5
--- /dev/null
+++ b/src/fsharp/FSharp.Compiler.Unittests/ManglingNameOfProvidedTypes.fs
@@ -0,0 +1,68 @@
+// Copyright (c) Microsoft Open Technologies, Inc.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
+namespace FSharp.Compiler.Unittests
+
+open System
+open System.Text
+open NUnit.Framework
+open Microsoft.FSharp.Compiler
+
+[<TestFixture>]
+type ManglingNamesOfProvidedTypesWithSingleParameter() = 
+    
+    [<Test>]
+    member this.MangleWithNonDefaultValue() = 
+        let mangled = 
+            PrettyNaming.computeMangledNameWithoutDefaultArgValues("MyNamespace.Test", [| "xyz" |], [| "Foo", Some "abc" |])
+        Assert.AreEqual("MyNamespace.Test,Foo=\"xyz\"", mangled)
+    
+    [<Test>]
+    member this.MangleWithDefaultValue() = 
+        let mangled = 
+            PrettyNaming.computeMangledNameWithoutDefaultArgValues("MyNamespace.Test", [| "xyz" |], [| "Foo", Some "xyz" |])
+        Assert.AreEqual("MyNamespace.Test", mangled)
+    
+    [<Test>]
+    member this.DemangleNonDefaultValue() = 
+        let name, parameters = PrettyNaming.demangleProvidedTypeName "MyNamespace.Test,Foo=\"xyz\""
+        Assert.AreEqual("MyNamespace.Test", name)
+        Assert.AreEqual([| "Foo", "xyz" |], parameters)
+    
+    [<Test>]
+    member this.DemangleDefaultValue() = 
+        let name, parameters = PrettyNaming.demangleProvidedTypeName "MyNamespace.Test,"
+        Assert.AreEqual("MyNamespace.Test", name)
+        Assert.AreEqual([||], parameters)
+
+    [<Test>]
+    member this.DemangleNewDefaultValue() = 
+        let name, parameters = PrettyNaming.demangleProvidedTypeName "MyNamespace.Test"
+        Assert.AreEqual("MyNamespace.Test", name)
+        Assert.AreEqual([||], parameters)
+
+[<TestFixture>]
+type ManglingNamesOfProvidedTypesWithMultipleParameter() = 
+    
+    [<Test>]
+    member this.MangleWithNonDefaultValue() = 
+        let mangled = 
+            PrettyNaming.computeMangledNameWithoutDefaultArgValues 
+                ("MyNamespace.Test", [| "xyz"; "abc" |], 
+                    [| "Foo", Some "foo"
+                       "Foo2", Some "foo2" |])
+        Assert.AreEqual("MyNamespace.Test,Foo=\"xyz\",Foo2=\"abc\"", mangled)
+    
+    [<Test>]
+    member this.MangleWithDefaultValue() = 
+        let mangled = 
+            PrettyNaming.computeMangledNameWithoutDefaultArgValues 
+                ("MyNamespace.Test", [| "xyz"; "abc" |], 
+                    [| "Foo", Some "xyz"
+                       "Foo2", Some "abc" |])
+        Assert.AreEqual("MyNamespace.Test", mangled)
+    
+    [<Test>]
+    member this.DemangleMultiParameter() = 
+        let name, parameters = PrettyNaming.demangleProvidedTypeName "TestType,Foo=\"xyz\",Foo2=\"abc\""
+        Assert.AreEqual("TestType", name)
+        Assert.AreEqual([| "Foo", "xyz"
+                           "Foo2", "abc" |], parameters)
\ No newline at end of file
diff --git a/src/fsharp/PrettyNaming.fs b/src/fsharp/PrettyNaming.fs
index 9b74deacf49bd07ff70d6a9046f4f8854bf304f0..84e3848095c43a460a0cc31f86c42572f4564260 100644
--- a/src/fsharp/PrettyNaming.fs
+++ b/src/fsharp/PrettyNaming.fs
@@ -445,16 +445,15 @@ module internal Microsoft.FSharp.Compiler.PrettyNaming
 
     let demangleProvidedTypeName (typeLogicalName:string) = 
         if typeLogicalName.Contains "," then 
-            let pieces = splitAroundQuotation typeLogicalName ',' 
-            if pieces.[1..] |> Array.forall (fun x -> tryDemangleStaticStringArg x |> Option.isSome) then
-                let argNamesAndValues = 
-                    pieces.[1..] |> Array.map (fun piece -> 
-                        match tryDemangleStaticStringArg piece with 
-                        | None -> raise (InvalidMangledStaticArg piece)
-                        | Some v -> v)
-                pieces.[0], argNamesAndValues
-            else 
-                typeLogicalName, [| |]
+            let pieces = splitAroundQuotation typeLogicalName ','
+            match pieces with
+            | [| x; "" |] -> x, [| |]
+            | _ ->
+                let argNamesAndValues = pieces.[1..] |> Array.choose tryDemangleStaticStringArg
+                if argNamesAndValues.Length = (pieces.Length - 1) then
+                    pieces.[0], argNamesAndValues
+                else
+                    typeLogicalName, [| |]
         else 
             typeLogicalName, [| |]
 
@@ -463,8 +462,20 @@ module internal Microsoft.FSharp.Compiler.PrettyNaming
             nonDefaultArgs
             |> Array.map mangleStaticStringArg
             |> String.concat ","
-        typeLogicalName+","+nonDefaultArgsText
 
-    //let testDemangleStaticStringArg() = 
-    //   for x in [ ""; "\""; "\"\""; "a"; "\\"; "\\\\"; "\\\""; "_"; "\"\"" ] do 
-    //      if demangleStaticStringArg (mangleStaticStringArg x) <> x then printfn "failed for <<%s>>" x
+        if nonDefaultArgsText = "" then
+            typeLogicalName
+        else
+            typeLogicalName + "," + nonDefaultArgsText
+
+
+    let computeMangledNameWithoutDefaultArgValues(nm,staticArgs,defaultArgValues) =
+        let nonDefaultArgs = 
+            (staticArgs,defaultArgValues) 
+            ||> Array.zip 
+            |> Array.choose (fun (staticArg, (defaultArgName, defaultArgValue)) -> 
+                let actualArgValue = string staticArg 
+                match defaultArgValue with 
+                | Some v when v = actualArgValue -> None
+                | _ -> Some (defaultArgName, actualArgValue))
+        mangleProvidedTypeName (nm, nonDefaultArgs)
\ No newline at end of file
diff --git a/src/fsharp/est.fs b/src/fsharp/est.fs
index 31c2198b727242d890f075ac1990956e5b0be992..59e513ebc0977a5244432cd1cdaec60303d57dc2 100644
--- a/src/fsharp/est.fs
+++ b/src/fsharp/est.fs
@@ -1262,16 +1262,7 @@ module internal ExtensionTyping =
             staticParams.PApply((fun ps ->  ps |> Array.map (fun sp -> sp.Name, (if sp.IsOptional then Some (string sp.RawDefaultValue) else None ))),range=m)
 
         let defaultArgValues = defaultArgValues.PUntaint(id,m)
-
-        let nonDefaultArgs = 
-            (staticArgs,defaultArgValues) 
-            ||> Array.zip 
-            |> Array.choose (fun (staticArg, (defaultArgName, defaultArgValue)) -> 
-                let actualArgValue = string  staticArg 
-                match defaultArgValue with 
-                | Some v when v = actualArgValue -> None
-                | _ -> Some (defaultArgName, actualArgValue))
-        PrettyNaming.mangleProvidedTypeName (nm, nonDefaultArgs)
+        PrettyNaming.computeMangledNameWithoutDefaultArgValues(nm,staticArgs,defaultArgValues)
 
     /// Apply the given provided method to the given static arguments (the arguments are assumed to have been sorted into application order)
     let TryApplyProvidedMethod(methBeforeArgs:Tainted<ProvidedMethodBase>, staticArgs:obj[], m:range) =