diff --git a/mozilla/layout/mathml/base/src/nsMathMLmoFrame.cpp b/mozilla/layout/mathml/base/src/nsMathMLmoFrame.cpp
index 243aefcf0c9..f9190b029da 100644
--- a/mozilla/layout/mathml/base/src/nsMathMLmoFrame.cpp
+++ b/mozilla/layout/mathml/base/src/nsMathMLmoFrame.cpp
@@ -974,6 +974,13 @@ nsMathMLmoFrame::ReflowDirtyChild(nsIPresShell* aPresShell,
   return ReLayoutChildren(target);
 }
 
+nsresult
+nsMathMLmoFrame::ChildListChanged(PRInt32 aModType)
+{
+  ProcessTextData(GetPresContext());
+  return nsMathMLContainerFrame::ChildListChanged(aModType);
+}
+
 NS_IMETHODIMP
 nsMathMLmoFrame::AttributeChanged(PRInt32         aNameSpaceID,
                                   nsIAtom*        aAttribute,
diff --git a/mozilla/layout/mathml/base/src/nsMathMLmoFrame.h b/mozilla/layout/mathml/base/src/nsMathMLmoFrame.h
index 75e3e68eb42..025bc5e5a23 100644
--- a/mozilla/layout/mathml/base/src/nsMathMLmoFrame.h
+++ b/mozilla/layout/mathml/base/src/nsMathMLmoFrame.h
@@ -84,6 +84,9 @@ public:
                    nsIAtom*        aAttribute,
                    PRInt32         aModType);
 
+  virtual nsresult
+  ChildListChanged(PRInt32 aModType);
+
   // This method is called by the parent frame to ask <mo> 
   // to stretch itself.
   NS_IMETHOD