diff --git a/idea/src/org/jetbrains/jet/plugin/highlighter/DeclarationHintSupport.java b/idea/src/org/jetbrains/jet/plugin/highlighter/DeclarationHintSupport.java
index 4b7636657c2..d6bc0dc2e31 100644
--- a/idea/src/org/jetbrains/jet/plugin/highlighter/DeclarationHintSupport.java
+++ b/idea/src/org/jetbrains/jet/plugin/highlighter/DeclarationHintSupport.java
@@ -25,6 +25,7 @@ import com.intellij.openapi.editor.EditorFactory;
 import com.intellij.openapi.editor.event.EditorMouseEvent;
 import com.intellij.openapi.editor.event.EditorMouseEventArea;
 import com.intellij.openapi.editor.event.EditorMouseMotionAdapter;
+import com.intellij.openapi.project.DumbService;
 import com.intellij.openapi.project.Project;
 import com.intellij.psi.PsiDocumentManager;
 import com.intellij.psi.PsiElement;
@@ -67,6 +68,10 @@ public class DeclarationHintSupport extends AbstractProjectComponent {
             PsiFile psiFile = PsiDocumentManager.getInstance(myProject).getPsiFile(editor.getDocument());
             if (psiFile == null || psiFile.getLanguage() != JetLanguage.INSTANCE) return;
 
+            if (DumbService.getInstance(psiFile.getProject()).isDumb()) {
+                return;
+            }
+
             JetFile jetFile = (JetFile) psiFile;
 
             int offset = editor.logicalPositionToOffset(editor.xyToLogicalPosition(e.getMouseEvent().getPoint()));