diff --git a/java/debugger/impl/src/com/intellij/debugger/jdi/StackFrameProxyImpl.java b/java/debugger/impl/src/com/intellij/debugger/jdi/StackFrameProxyImpl.java
index cc0a18951971..a443b6c03dbd 100644
--- a/java/debugger/impl/src/com/intellij/debugger/jdi/StackFrameProxyImpl.java
+++ b/java/debugger/impl/src/com/intellij/debugger/jdi/StackFrameProxyImpl.java
@@ -86,6 +86,7 @@ public class StackFrameProxyImpl extends JdiProxy implements StackFrameProxy {
 
   @Override
   public boolean isValid() {
+    DebuggerManagerThreadImpl.assertIsManagerThread();
     if (!super.isValid()) {
       return false;
     }