diff --git a/src/Undo.cpp b/src/Undo.cpp
index 143af4e83f..a479728ebd 100644
--- a/src/Undo.cpp
+++ b/src/Undo.cpp
@@ -643,6 +643,13 @@ void Undo::recordUndoFullBuffer(CursorData const & cur)
 
 /// UndoGroupHelper class stuff
 
+/** FIXME: handle restarted groups
+ * It may happen that the buffers are visited in order buffer1,
+ * buffer2, buffer1. In this case, we want to have only one undo group
+ * in buffer1. One solution is to replace buffer_ with a set<Buffer*>,
+ * but I am not sure yet how to do it. A use case is
+ * InsetLabel::updateReferences.
+ */
 void UndoGroupHelper::resetBuffer(Buffer * buf)
 {
 	if (buf == buffer_)
diff --git a/src/Undo.h b/src/Undo.h
index 59f3ca44fc..70897bfa28 100644
--- a/src/Undo.h
+++ b/src/Undo.h
@@ -135,7 +135,7 @@ private:
  */
 class UndoGroupHelper {
 public:
-	UndoGroupHelper(Buffer * buf) : buffer_(0)
+	UndoGroupHelper(Buffer * buf = 0) : buffer_(0)
 	{
 		resetBuffer(buf);
 	}
diff --git a/src/insets/InsetLabel.cpp b/src/insets/InsetLabel.cpp
index 553c6d7b96..f4a6f08eb6 100644
--- a/src/insets/InsetLabel.cpp
+++ b/src/insets/InsetLabel.cpp
@@ -109,11 +109,13 @@ void InsetLabel::updateLabelAndRefs(docstring const & new_label,
 void InsetLabel::updateReferences(docstring const & old_label,
 		docstring const & new_label)
 {
+	UndoGroupHelper ugh;
 	Buffer::References const & refs = buffer().references(old_label);
 	Buffer::References::const_iterator it = refs.begin();
 	Buffer::References::const_iterator end = refs.end();
 	for (; it != end; ++it) {
-		buffer().undo().recordUndo(CursorData(it->second));
+		ugh.resetBuffer(it->second.buffer());
+		it->second.buffer()->undo().recordUndo(CursorData(it->second));
 		if (it->first->lyxCode() == MATH_REF_CODE) {
 			InsetMathRef * mi = it->first->asInsetMath()->asRefInset();
 			mi->changeTarget(new_label);
diff --git a/status.22x b/status.22x
index e5ee170235..cb2ba55f55 100644
--- a/status.22x
+++ b/status.22x
@@ -84,6 +84,8 @@ What's new
 
 - Avoid crash when selecting long text (bug 10324).
 
+- Fix crash with undo and child documents (bug 10643).
+
 - Remove duplicate entries from the Symbols dialog (bug 10644).
 
 - Always show the float type in the float inset label (bug 10618).