diff --git a/platform/core-impl/src/com/intellij/psi/impl/source/PsiFileImpl.java b/platform/core-impl/src/com/intellij/psi/impl/source/PsiFileImpl.java
index 7c046953b4a7..70996679e896 100644
--- a/platform/core-impl/src/com/intellij/psi/impl/source/PsiFileImpl.java
+++ b/platform/core-impl/src/com/intellij/psi/impl/source/PsiFileImpl.java
@@ -1010,6 +1010,10 @@ public abstract class PsiFileImpl extends ElementBase implements PsiFileEx, PsiF
         }
 
         StubElement currentStubTree = ((IStubFileElementType)contentElementType).getBuilder().buildStubTree(this);
+        if (currentStubTree == null) {
+          throw new AssertionError("Stub tree wasn't built for " + contentElementType + "; file: " + this);
+        }
+
         tree = new StubTree((PsiFileStub)currentStubTree);
         tree.setDebugInfo("created in calcStubTree");
         try {