diff --git a/idea/src/org/jetbrains/jet/codegen/ExpressionCodegen.java b/idea/src/org/jetbrains/jet/codegen/ExpressionCodegen.java
index 3f17fcb2d2a17c67172d2f0c602bba77b7eff2d7..cc0a20b79f325239a9b6544d72756cd048cc94c6 100644
--- a/idea/src/org/jetbrains/jet/codegen/ExpressionCodegen.java
+++ b/idea/src/org/jetbrains/jet/codegen/ExpressionCodegen.java
@@ -722,13 +722,17 @@ public class ExpressionCodegen extends JetVisitor {
                             methodDescriptor.getDescriptor());
                 }
                 else {
-                    methodDescriptor = typeMapper.mapSignature((JetFunction) declarationPsiElement);
-                    if (functionParent instanceof NamespaceDescriptorImpl && declarationPsiElement instanceof JetFunction) {
+                    final JetFunction jetFunction = (JetFunction) declarationPsiElement;
+                    methodDescriptor = typeMapper.mapSignature(jetFunction);
+                    if (functionParent instanceof NamespaceDescriptorImpl) {
+                        if (jetFunction.getReceiverTypeRef() != null) {
+                            ensureReceiverOnStack(expression);
+                        }
                         pushMethodArguments(expression, methodDescriptor);
                         final String owner = NamespaceCodegen.getJVMClassName(DescriptorRenderer.getFQName(functionParent));
                         v.invokestatic(owner, methodDescriptor.getName(), methodDescriptor.getDescriptor());
                     }
-                    else if (functionParent instanceof ClassDescriptor && declarationPsiElement instanceof JetFunction) {
+                    else if (functionParent instanceof ClassDescriptor) {
                         ensureReceiverOnStack(expression);
                         pushMethodArguments(expression, methodDescriptor);
                         final String owner = JetTypeMapper.jvmNameForInterface((ClassDescriptor) functionParent);
diff --git a/idea/testData/codegen/extensionFunctions/whenFail.jet b/idea/testData/codegen/extensionFunctions/whenFail.jet
new file mode 100644
index 0000000000000000000000000000000000000000..252fe893a86477c4eef1690676b10f6c2bd2d4a0
--- /dev/null
+++ b/idea/testData/codegen/extensionFunctions/whenFail.jet
@@ -0,0 +1,14 @@
+fun StringBuilder.takeFirst(): Char {
+  if (this.length() == 0) return '\0'
+  val c = this.charAt(0)
+  this.deleteCharAt(0)
+  return c
+}
+
+fun foo(expr: StringBuilder): Int {
+  val c = expr.takeFirst()
+  when(c) {
+    '\0' => throw new Exception("zero")
+    else => throw new Exception("nonzero" + c)
+  }
+}
diff --git a/idea/tests/org/jetbrains/jet/codegen/CodegenTestCase.java b/idea/tests/org/jetbrains/jet/codegen/CodegenTestCase.java
index 71453d139798a3e79278c17b73c08962232e17d4..b8d2823880c69f70754839de3c40126260735a4e 100644
--- a/idea/tests/org/jetbrains/jet/codegen/CodegenTestCase.java
+++ b/idea/tests/org/jetbrains/jet/codegen/CodegenTestCase.java
@@ -12,9 +12,8 @@ import org.jetbrains.jet.lang.psi.JetNamespace;
 import org.jetbrains.jet.lang.resolve.AnalyzingUtils;
 import org.jetbrains.jet.parsing.JetParsingTest;
 
-import javax.swing.JComponent;
+import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
-import java.nio.channels.NonWritableChannelException;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
@@ -25,6 +24,17 @@ import java.util.Map;
 public abstract class CodegenTestCase extends LightCodeInsightFixtureTestCase {
     private MyClassLoader myClassLoader;
 
+    protected static void assertThrows(Method foo, Class<? extends Throwable> exceptionClass, Object instance, Object... args) throws IllegalAccessException {
+        boolean caught = false;
+        try {
+            foo.invoke(instance, args);
+        }
+        catch(InvocationTargetException ex) {
+            caught = exceptionClass.isInstance(ex.getTargetException());
+        }
+        assertTrue(caught);
+    }
+
     @Override
     protected void setUp() throws Exception {
         super.setUp();
@@ -128,14 +138,19 @@ public abstract class CodegenTestCase extends LightCodeInsightFixtureTestCase {
     }
 
     protected Codegens generateClassesInFile() {
-        Codegens state = new Codegens(getProject(), false);
-        JetFile jetFile = (JetFile) myFixture.getFile();
-        AnalyzingUtils.checkForSyntacticErrors(jetFile);
-        final JetNamespace namespace = jetFile.getRootNamespace();
-
-        NamespaceCodegen codegen = state.forNamespace(namespace);
-        codegen.generate(namespace);
-        return state;
+        try {
+            Codegens state = new Codegens(getProject(), false);
+            JetFile jetFile = (JetFile) myFixture.getFile();
+            AnalyzingUtils.checkForSyntacticErrors(jetFile);
+            final JetNamespace namespace = jetFile.getRootNamespace();
+
+            NamespaceCodegen codegen = state.forNamespace(namespace);
+            codegen.generate(namespace);
+            return state;
+        } catch (RuntimeException e) {
+            System.out.println(generateToText());
+            throw e;
+        }
     }
 
     protected Method generateFunction() {
diff --git a/idea/tests/org/jetbrains/jet/codegen/ExtensionFunctionsTest.java b/idea/tests/org/jetbrains/jet/codegen/ExtensionFunctionsTest.java
index 59d78daf88a79f27adb135bfafc06d65e66a8906..3305c6f551e57cd1a73c546ce7cc68f8cf5b512e 100644
--- a/idea/tests/org/jetbrains/jet/codegen/ExtensionFunctionsTest.java
+++ b/idea/tests/org/jetbrains/jet/codegen/ExtensionFunctionsTest.java
@@ -17,4 +17,10 @@ public class ExtensionFunctionsTest extends CodegenTestCase {
         final Character c = (Character) foo.invoke(null);
         assertEquals('f', c.charValue());
     }
+
+    public void testWhenFail() throws Exception {
+        loadFile();
+        Method foo = generateFunction("foo");
+        assertThrows(foo, Exception.class, null, new StringBuilder());
+    }
 }
diff --git a/idea/tests/org/jetbrains/jet/codegen/PatternMatchingTest.java b/idea/tests/org/jetbrains/jet/codegen/PatternMatchingTest.java
index 6f27ac9ebf689b59b774fb0072b9cd7f0b9ce710..5ac5d30fb4c6819d5e864ef6025c154af649c7c4 100644
--- a/idea/tests/org/jetbrains/jet/codegen/PatternMatchingTest.java
+++ b/idea/tests/org/jetbrains/jet/codegen/PatternMatchingTest.java
@@ -2,7 +2,6 @@ package org.jetbrains.jet.codegen;
 
 import jet.NoPatternMatchedException;
 
-import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
 
 /**
@@ -25,14 +24,7 @@ public class PatternMatchingTest extends CodegenTestCase {
         loadFile();
         Method foo = generateFunction();
         assertTrue((Boolean) foo.invoke(null, 0));
-        boolean caught = false;
-        try {
-            foo.invoke(null, 1);
-        }
-        catch(InvocationTargetException ex) {
-            caught = ex.getTargetException() instanceof NoPatternMatchedException;
-        }
-        assertTrue(caught);
+        assertThrows(foo, NoPatternMatchedException.class, null, 1);
     }
 
     public void testPattern() throws Exception {