diff --git a/platform/platform-impl/src/com/intellij/openapi/editor/impl/FoldingModelImpl.java b/platform/platform-impl/src/com/intellij/openapi/editor/impl/FoldingModelImpl.java
index d3dd779431af..f4540b7d7309 100644
--- a/platform/platform-impl/src/com/intellij/openapi/editor/impl/FoldingModelImpl.java
+++ b/platform/platform-impl/src/com/intellij/openapi/editor/impl/FoldingModelImpl.java
@@ -561,6 +561,7 @@ public class FoldingModelImpl implements FoldingModelEx, PrioritizedInternalDocu
 
   @Override
   public void beforeDocumentChange(DocumentEvent event) {
+    if (myIsBatchFoldingProcessing) LOG.error("Document changes are not allowed during batch folding update");
     myDocumentChangeProcessed = false;
   }
 
diff --git a/platform/platform-impl/src/com/intellij/openapi/editor/impl/view/EditorSizeManager.java b/platform/platform-impl/src/com/intellij/openapi/editor/impl/view/EditorSizeManager.java
index 5b6d786efd80..b997117c9de8 100644
--- a/platform/platform-impl/src/com/intellij/openapi/editor/impl/view/EditorSizeManager.java
+++ b/platform/platform-impl/src/com/intellij/openapi/editor/impl/view/EditorSizeManager.java
@@ -378,6 +378,8 @@ class EditorSizeManager extends InlayModel.SimpleAdapter implements PrioritizedD
   }
 
   void textLayoutPerformed(int startOffset, int endOffset) {
+    assert 0 <= startOffset && startOffset < endOffset && endOffset <= myDocument.getTextLength() 
+      : "startOffset=" + startOffset + ", endOffset=" + endOffset;
     if (myDocument.isInBulkUpdate()) return;
     if (myEditor.getFoldingModel().isInBatchFoldingOperation()) {
       myDeferredRanges.add(new TextRange(startOffset, endOffset));