diff --git a/platform/platform-impl/src/com/intellij/openapi/fileEditor/impl/IdeDocumentHistoryImpl.java b/platform/platform-impl/src/com/intellij/openapi/fileEditor/impl/IdeDocumentHistoryImpl.java
index a21e0706714d..03e26c82f8d1 100644
--- a/platform/platform-impl/src/com/intellij/openapi/fileEditor/impl/IdeDocumentHistoryImpl.java
+++ b/platform/platform-impl/src/com/intellij/openapi/fileEditor/impl/IdeDocumentHistoryImpl.java
@@ -1,4 +1,6 @@
-// Copyright 2000-2017 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
+/*
+ * Copyright 2000-2017 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
+ */
 package com.intellij.openapi.fileEditor.impl;
 
 import com.intellij.ide.ui.UISettings;
@@ -180,6 +182,7 @@ public class IdeDocumentHistoryImpl extends IdeDocumentHistory implements Projec
     Document document = e.getDocument();
     final VirtualFile file = getFileDocumentManager().getFile(document);
     if (file != null && !(file instanceof LightVirtualFile) && !ApplicationManager.getApplication().hasWriteAction(ExternalChangeAction.class)) {
+      if (!ApplicationManager.getApplication().isDispatchThread()) LOG.error("Document update for physical file not in EDT: " + file);
       myCurrentCommandHasChanges = true;
       myChangedFilesInCurrentCommand.add(file);
     }