diff --git a/platform/core-impl/src/com/intellij/openapi/vfs/impl/VirtualFileManagerImpl.java b/platform/core-impl/src/com/intellij/openapi/vfs/impl/VirtualFileManagerImpl.java
index e05d8fbe0f09..fa67da9afd05 100644
--- a/platform/core-impl/src/com/intellij/openapi/vfs/impl/VirtualFileManagerImpl.java
+++ b/platform/core-impl/src/com/intellij/openapi/vfs/impl/VirtualFileManagerImpl.java
@@ -86,7 +86,7 @@ public class VirtualFileManagerImpl extends VirtualFileManagerEx {
     if (protocol == null) return null;
     List<VirtualFileSystem> systems = myCollector.forKey(protocol);
     if (systems.isEmpty()) return null;
-    LOG.assertTrue(systems.size() == 1);
+    LOG.assertTrue(systems.size() == 1, protocol + ": " + systems);
     return systems.get(0);
   }