diff --git a/platform/indexing-impl/src/com/intellij/psi/stubs/StubProcessingHelperBase.java b/platform/indexing-impl/src/com/intellij/psi/stubs/StubProcessingHelperBase.java
index a01cfb1c316f..a97ae21b1d81 100644
--- a/platform/indexing-impl/src/com/intellij/psi/stubs/StubProcessingHelperBase.java
+++ b/platform/indexing-impl/src/com/intellij/psi/stubs/StubProcessingHelperBase.java
@@ -55,7 +55,7 @@ public abstract class StubProcessingHelperBase {
           }
           else {
             customStubs = true;
-            assert BinaryFileStubBuilders.INSTANCE.forFileType(psiFile.getFileType()) != null;
+            assert BinaryFileStubBuilders.INSTANCE.forFileType(psiFile.getFileType()) != null : "unable to get stub builder for " + psiFile.getFileType();
           }
         }
       }