diff --git a/java/idea-ui/src/com/intellij/openapi/roots/ui/configuration/ContentEntriesEditor.java b/java/idea-ui/src/com/intellij/openapi/roots/ui/configuration/ContentEntriesEditor.java
index 0726dd55f03f..9bb8ef5c9c5c 100644
--- a/java/idea-ui/src/com/intellij/openapi/roots/ui/configuration/ContentEntriesEditor.java
+++ b/java/idea-ui/src/com/intellij/openapi/roots/ui/configuration/ContentEntriesEditor.java
@@ -17,6 +17,7 @@ package com.intellij.openapi.roots.ui.configuration;
 
 import com.intellij.openapi.options.ConfigurationException;
 import com.intellij.openapi.roots.LanguageLevelModuleExtensionImpl;
+import org.jetbrains.annotations.NotNull;
 
 import javax.swing.*;
 import java.awt.*;
@@ -47,6 +48,7 @@ public class ContentEntriesEditor extends JavaContentEntriesEditor {
   @Override
   protected void addAdditionalSettingsToPanel(final JPanel mainPanel) {
     myLanguageLevelConfigurable = new LanguageLevelConfigurable(myProject) {
+      @NotNull
       @Override
       public LanguageLevelModuleExtensionImpl getLanguageLevelExtension() {
         return getModel().getModuleExtension(LanguageLevelModuleExtensionImpl.class);
diff --git a/java/idea-ui/src/com/intellij/openapi/roots/ui/configuration/LanguageLevelConfigurable.java b/java/idea-ui/src/com/intellij/openapi/roots/ui/configuration/LanguageLevelConfigurable.java
index ad7ca4a1f8d7..43fb9cd7d21c 100644
--- a/java/idea-ui/src/com/intellij/openapi/roots/ui/configuration/LanguageLevelConfigurable.java
+++ b/java/idea-ui/src/com/intellij/openapi/roots/ui/configuration/LanguageLevelConfigurable.java
@@ -89,5 +89,6 @@ public abstract class LanguageLevelConfigurable implements UnnamedConfigurable {
     myLanguageLevelCombo = null;
   }
 
+  @NotNull
   public abstract LanguageLevelModuleExtensionImpl getLanguageLevelExtension();
 }