diff --git a/compiler/frontend/src/org/jetbrains/jet/lang/resolve/lazy/ResolveSession.java b/compiler/frontend/src/org/jetbrains/jet/lang/resolve/lazy/ResolveSession.java
index 87935b97cf9..bce8cf7619c 100644
--- a/compiler/frontend/src/org/jetbrains/jet/lang/resolve/lazy/ResolveSession.java
+++ b/compiler/frontend/src/org/jetbrains/jet/lang/resolve/lazy/ResolveSession.java
@@ -147,6 +147,9 @@ public class ResolveSession {
         Name name = classOrObject.getNameAsName();
         assert name != null : "Name is null for " + classOrObject + " " + classOrObject.getText();
         ClassifierDescriptor classifier = resolutionScope.getClassifier(name);
+        if (classifier == null) {
+            throw new IllegalArgumentException("Could not find a classifier for " + classOrObject + " " + classOrObject.getText());
+        }
         return (ClassDescriptor) classifier;
     }