diff --git a/compiler/backend/src/org/jetbrains/jet/codegen/ExpressionCodegen.java b/compiler/backend/src/org/jetbrains/jet/codegen/ExpressionCodegen.java
index f47afb4ae47..2e9c4506b79 100644
--- a/compiler/backend/src/org/jetbrains/jet/codegen/ExpressionCodegen.java
+++ b/compiler/backend/src/org/jetbrains/jet/codegen/ExpressionCodegen.java
@@ -2550,24 +2550,40 @@ If finally block is present, its last expression is the value of try expression.
         }
         else {
             JetTypeReference typeReference = expression.getRight();
-            JetType jetType = bindingContext.get(BindingContext.TYPE, typeReference);
-            assert jetType != null;
-            DeclarationDescriptor descriptor = jetType.getConstructor().getDeclarationDescriptor();
+            JetType rightType = bindingContext.get(BindingContext.TYPE, typeReference);
+            Type rightTypeAsm = boxType(asmType(rightType));
+            assert rightType != null;
+            JetExpression left = expression.getLeft();
+            JetType leftType = bindingContext.get(BindingContext.EXPRESSION_TYPE, left);
+            DeclarationDescriptor descriptor = rightType.getConstructor().getDeclarationDescriptor();
             if (descriptor instanceof ClassDescriptor || descriptor instanceof TypeParameterDescriptor) {
-                Type type = boxType(asmType(jetType));
-                generateInstanceOf(StackValue.expression(TYPE_OBJECT, expression.getLeft(), this), jetType, true);
-                Label isInstance = new Label();
-                v.ifne(isInstance);
-                v.pop();
-                if (opToken == JetTokens.AS_SAFE) {
-                    v.aconst(null);
+                StackValue value = genQualified(receiver, left);
+                value.put(JetTypeMapper.boxType(value.type), v);
+                assert leftType != null;
+
+                if (opToken != JetTokens.AS_SAFE) {
+                    if(leftType.isNullable()) {
+                        if (!rightType.isNullable()) {
+                            v.dup();
+                            Label nonnull = new Label();
+                            v.ifnonnull(nonnull);
+                            throwNewException(CLASS_TYPE_CAST_EXCEPTION);
+                            v.mark(nonnull);
+                        }
+                    }
                 }
                 else {
-                    throwNewException(CLASS_TYPE_CAST_EXCEPTION);
+                    v.dup();
+                    v.instanceOf(rightTypeAsm);
+                    Label ok = new Label();
+                    v.ifne(ok);
+                    v.pop();
+                    v.aconst(null);
+                    v.mark(ok);
                 }
-                v.mark(isInstance);
-                v.checkcast(type);
-                return StackValue.onStack(type);
+
+                v.checkcast(rightTypeAsm);
+                return StackValue.onStack(rightTypeAsm);
             }
             else {
                 throw new UnsupportedOperationException("don't know how to handle non-class types in as/as?");
diff --git a/compiler/tests/org/jetbrains/jet/codegen/TypeInfoTest.java b/compiler/tests/org/jetbrains/jet/codegen/TypeInfoTest.java
index fbb3d506d0a..06e2cb575b1 100644
--- a/compiler/tests/org/jetbrains/jet/codegen/TypeInfoTest.java
+++ b/compiler/tests/org/jetbrains/jet/codegen/TypeInfoTest.java
@@ -43,7 +43,7 @@ public class TypeInfoTest extends CodegenTestCase {
         Method foo = generateFunction();
         Runnable r = newRunnable();
         assertSame(r, foo.invoke(null, r));
-        assertThrows(foo, TypeCastException.class, null, new Object());
+        assertThrows(foo, ClassCastException.class, null, new Object());
     }
 
     public void testIsOperator() throws Exception {
diff --git a/idea/src/org/jetbrains/jet/plugin/libraries/JetContentBasedFileSubstitutor.java b/idea/src/org/jetbrains/jet/plugin/libraries/JetContentBasedFileSubstitutor.java
index 30c49172d5a..b7652072076 100644
--- a/idea/src/org/jetbrains/jet/plugin/libraries/JetContentBasedFileSubstitutor.java
+++ b/idea/src/org/jetbrains/jet/plugin/libraries/JetContentBasedFileSubstitutor.java
@@ -61,7 +61,6 @@ public class JetContentBasedFileSubstitutor implements ContentBasedClassFileProc
     }
 
     @Nullable
-    @Override
     public PsiFile getDecompiledPsiFile(PsiFile psiFile) {
         return JetDecompiledData.getDecompiledData((ClsFileImpl) psiFile).getJetFile();
     }
diff --git a/idea/src/org/jetbrains/jet/plugin/run/JetRunConfigurationProducer.java b/idea/src/org/jetbrains/jet/plugin/run/JetRunConfigurationProducer.java
index e1e772f448b..2270039f2e6 100644
--- a/idea/src/org/jetbrains/jet/plugin/run/JetRunConfigurationProducer.java
+++ b/idea/src/org/jetbrains/jet/plugin/run/JetRunConfigurationProducer.java
@@ -21,6 +21,7 @@ import com.intellij.execution.RunnerAndConfigurationSettings;
 import com.intellij.execution.actions.ConfigurationContext;
 import com.intellij.execution.junit.RuntimeConfigurationProducer;
 import com.intellij.openapi.module.Module;
+import com.intellij.openapi.util.Comparing;
 import com.intellij.openapi.util.text.StringUtil;
 import com.intellij.psi.PsiElement;
 import com.intellij.psi.PsiFile;
@@ -56,19 +57,31 @@ public class JetRunConfigurationProducer extends RuntimeConfigurationProducer im
             return null;
         }
 
+        FqName startClassFQName = getStartClassFQName(location);
+        if (startClassFQName == null) {
+            return null;
+        }
+
+        return createConfigurationByQName(module, configurationContext, startClassFQName);
+    }
+
+    @Nullable
+    private FqName getStartClassFQName(Location location) {
         PsiFile psiFile = location.getPsiElement().getContainingFile();
         if (psiFile instanceof JetFile) {
             JetFile jetFile = (JetFile) psiFile;
             if (JetMainDetector.hasMain(jetFile.getDeclarations())) {
                 mySourceElement = jetFile;
                 FqName fqName = JetPsiUtil.getFQName(jetFile);
-                FqName className = fqName.child(JvmAbi.PACKAGE_CLASS);
-                return createConfigurationByQName(module, configurationContext, className);
+                return fqName.child(JvmAbi.PACKAGE_CLASS);
             }
         }
+
         return null;
     }
 
+
+    @NotNull
     private RunnerAndConfigurationSettings createConfigurationByQName(
             @NotNull Module module,
             ConfigurationContext context,
@@ -82,6 +95,30 @@ public class JetRunConfigurationProducer extends RuntimeConfigurationProducer im
         return settings;
     }
 
+    @Override
+    protected RunnerAndConfigurationSettings findExistingByElement(
+            Location location,
+            @NotNull RunnerAndConfigurationSettings[] existingConfigurations,
+            ConfigurationContext context
+    ) {
+        FqName startClassFQName = getStartClassFQName(location);
+        if (startClassFQName == null) {
+            return null;
+        }
+
+        for (RunnerAndConfigurationSettings existingConfiguration : existingConfigurations) {
+            if (existingConfiguration.getType() instanceof JetRunConfigurationType) {
+                JetRunConfiguration jetConfiguration = (JetRunConfiguration)existingConfiguration.getConfiguration();
+                if (Comparing.equal(jetConfiguration.settings().getMainClassName(), startClassFQName.getFqName())) {
+                    if (Comparing.equal(location.getModule(), jetConfiguration.getConfigurationModule().getModule())) {
+                        return existingConfiguration;
+                    }
+                }
+            }
+        }
+        return null;
+    }
+
     @Override
     public int compareTo(Object o) {
         return PREFERED;