diff --git a/idea/src/org/jetbrains/jet/plugin/debugger/evaluate/KotlinEvaluationBuilder.kt b/idea/src/org/jetbrains/jet/plugin/debugger/evaluate/KotlinEvaluationBuilder.kt
index 328ea6837a6..f096aef72e6 100644
--- a/idea/src/org/jetbrains/jet/plugin/debugger/evaluate/KotlinEvaluationBuilder.kt
+++ b/idea/src/org/jetbrains/jet/plugin/debugger/evaluate/KotlinEvaluationBuilder.kt
@@ -325,7 +325,7 @@ fun EvaluationContextImpl.findLocalVariable(name: String, asmType: Type?, checkT
 
         val thisDesc = value.asmType.getClassDescriptor(project)
         val expDesc = asmType.getClassDescriptor(project)
-        return thisDesc != null && expDesc != null && DescriptorUtils.isSubclass(thisDesc, expDesc)
+        return thisDesc != null && expDesc != null && runReadAction { DescriptorUtils.isSubclass(thisDesc, expDesc) }!!
     }