diff --git a/idea/src/org/jetbrains/jet/plugin/JetQuickDocumentationProvider.java b/idea/src/org/jetbrains/jet/plugin/JetQuickDocumentationProvider.java
index a0efebdf3fd..94ec8fec1f2 100644
--- a/idea/src/org/jetbrains/jet/plugin/JetQuickDocumentationProvider.java
+++ b/idea/src/org/jetbrains/jet/plugin/JetQuickDocumentationProvider.java
@@ -21,10 +21,10 @@ import com.intellij.lang.documentation.AbstractDocumentationProvider;
 import com.intellij.lang.java.JavaDocumentationProvider;
 import com.intellij.openapi.project.Project;
 import com.intellij.openapi.util.text.StringUtil;
+import com.intellij.openapi.vfs.VirtualFile;
 import com.intellij.psi.PsiElement;
 import com.intellij.psi.PsiWhiteSpace;
 import com.intellij.psi.impl.compiled.ClsClassImpl;
-import com.intellij.psi.impl.compiled.ClsFileImpl;
 import com.intellij.psi.tree.IElementType;
 import com.intellij.psi.util.PsiTreeUtil;
 import org.jetbrains.annotations.NotNull;
@@ -35,7 +35,7 @@ import org.jetbrains.jet.lang.descriptors.DeclarationDescriptor;
 import org.jetbrains.jet.lang.psi.*;
 import org.jetbrains.jet.lang.resolve.BindingContext;
 import org.jetbrains.jet.lang.resolve.BindingContextUtils;
-import org.jetbrains.jet.plugin.libraries.JetDecompiledData;
+import org.jetbrains.jet.plugin.libraries.DecompiledUtils;
 import org.jetbrains.jet.plugin.project.AnalyzerFacadeWithCache;
 import org.jetbrains.jet.plugin.references.BuiltInsReferenceResolver;
 import org.jetbrains.jet.renderer.DescriptorRenderer;
@@ -117,7 +117,8 @@ public class JetQuickDocumentationProvider extends AbstractDocumentationProvider
         if (JetLanguage.INSTANCE == declaration.getLanguage()) return true;
         ClsClassImpl clsClass = PsiTreeUtil.getParentOfType(declaration, ClsClassImpl.class);
         if (clsClass == null) return false;
-        return JetDecompiledData.isKotlinFile((ClsFileImpl) clsClass.getContainingFile());
+        VirtualFile file = clsClass.getContainingFile().getVirtualFile();
+        return file != null && DecompiledUtils.isKotlinCompiledFile(file);
     }
 
     @Override
diff --git a/idea/src/org/jetbrains/jet/plugin/libraries/DecompiledUtils.java b/idea/src/org/jetbrains/jet/plugin/libraries/DecompiledUtils.java
new file mode 100644
index 00000000000..4612b18b4dd
--- /dev/null
+++ b/idea/src/org/jetbrains/jet/plugin/libraries/DecompiledUtils.java
@@ -0,0 +1,36 @@
+/*
+ * Copyright 2010-2013 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.jetbrains.jet.plugin.libraries;
+
+import com.intellij.openapi.fileTypes.StdFileTypes;
+import com.intellij.openapi.vfs.VirtualFile;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.jet.lang.resolve.java.resolver.KotlinClassFileHeader;
+
+public final class DecompiledUtils {
+
+    public static boolean isKotlinCompiledFile(@NotNull VirtualFile file) {
+        if (!StdFileTypes.CLASS.getDefaultExtension().equals(file.getExtension())) {
+            return false;
+        }
+        //TODO: check index
+        return KotlinClassFileHeader.readKotlinHeaderFromClassFile(file).isKotlinCompiledFile();
+    }
+
+    private DecompiledUtils() {
+    }
+}