diff --git a/layout/mathml/nsMathMLmactionFrame.cpp b/layout/mathml/nsMathMLmactionFrame.cpp
index d4b383d15727..259143ee8c16 100644
--- a/layout/mathml/nsMathMLmactionFrame.cpp
+++ b/layout/mathml/nsMathMLmactionFrame.cpp
@@ -71,6 +71,25 @@
 #define NS_MATHML_ACTION_TYPE_TOOLTIP      3 // unsupported
 
 
+// helper function to parse actiontype attribute
+static PRInt32
+GetActionType(nsIContent* aContent)
+{
+  nsAutoString value;
+
+  if (aContent)
+    aContent->GetAttr(kNameSpaceID_None, nsGkAtoms::actiontype_, value);
+
+  if (value.EqualsLiteral("toggle"))
+    return NS_MATHML_ACTION_TYPE_TOGGLE;
+  if (value.EqualsLiteral("statusline"))
+    return NS_MATHML_ACTION_TYPE_STATUSLINE;
+  if (value.EqualsLiteral("tooltip"))
+    return NS_MATHML_ACTION_TYPE_TOOLTIP;
+
+  return NS_MATHML_ACTION_TYPE_NONE;
+}
+
 nsIFrame*
 NS_NewMathMLmactionFrame(nsIPresShell* aPresShell, nsStyleContext* aContext)
 {
@@ -98,34 +117,12 @@ nsMathMLmactionFrame::Init(nsIContent*      aContent,
                            nsIFrame*        aParent,
                            nsIFrame*        aPrevInFlow)
 {
-  nsAutoString value, prefix;
-
   // Init our local attributes
 
   mChildCount = -1; // these will be updated in GetSelectedFrame()
   mSelection = 0;
   mSelectedFrame = nsnull;
-  nsRefPtr<nsStyleContext> newStyleContext;
-
-  mActionType = NS_MATHML_ACTION_TYPE_NONE;
-  aContent->GetAttr(kNameSpaceID_None, nsGkAtoms::actiontype_, value);
-  if (!value.IsEmpty()) {
-    if (value.EqualsLiteral("toggle"))
-      mActionType = NS_MATHML_ACTION_TYPE_TOGGLE;
-
-    // XXX use goto to jump out of these if?
-
-    if (NS_MATHML_ACTION_TYPE_NONE == mActionType) {
-      // expected tooltip prefix (8ch)...
-      if (8 < value.Length() && 0 == value.Find("tooltip#"))
-        mActionType = NS_MATHML_ACTION_TYPE_TOOLTIP;
-    }
-
-    if (NS_MATHML_ACTION_TYPE_NONE == mActionType) {
-      if (value.EqualsLiteral("statusline"))
-        mActionType = NS_MATHML_ACTION_TYPE_STATUSLINE;
-    }
-  }
+  mActionType = GetActionType(aContent);
 
   // Let the base class do the rest
   return nsMathMLContainerFrame::Init(aContent, aParent, aPrevInFlow);
@@ -247,6 +244,45 @@ nsMathMLmactionFrame::SetInitialChildList(ChildListID     aListID,
   return rv;
 }
 
+NS_IMETHODIMP
+nsMathMLmactionFrame::AttributeChanged(PRInt32  aNameSpaceID,
+                                       nsIAtom* aAttribute,
+                                       PRInt32  aModType)
+{
+  bool needsReflow = false;
+
+  if (aAttribute == nsGkAtoms::actiontype_) {
+    // updating mActionType ...
+    PRInt32 oldActionType = mActionType;
+    mActionType = GetActionType(mContent);
+
+    // We have to initiate a reflow only when changing actiontype
+    // from toggle or to toggle.
+    if (oldActionType == NS_MATHML_ACTION_TYPE_TOGGLE || 
+          mActionType == NS_MATHML_ACTION_TYPE_TOGGLE) {
+      needsReflow = true;
+    }
+  } else if (aAttribute == nsGkAtoms::selection_) {
+    // When the selection attribute is changed we have to initiate a reflow
+    // only when actiontype is toggle.
+    if (NS_MATHML_ACTION_TYPE_TOGGLE == mActionType) {
+      needsReflow = true;
+    }
+  } else {
+    // let the base class handle other attribute changes
+    return 
+      nsMathMLContainerFrame::AttributeChanged(aNameSpaceID, 
+                                               aAttribute, aModType);
+  }
+
+  if (needsReflow) {
+    PresContext()->PresShell()->
+      FrameNeedsReflow(this, nsIPresShell::eTreeChange, NS_FRAME_IS_DIRTY);
+  }
+
+  return NS_OK;
+}
+
 //  Only paint the selected child...
 NS_IMETHODIMP
 nsMathMLmactionFrame::BuildDisplayList(nsDisplayListBuilder*   aBuilder,
diff --git a/layout/mathml/nsMathMLmactionFrame.h b/layout/mathml/nsMathMLmactionFrame.h
index ce18efdf967b..8dcdcee78194 100644
--- a/layout/mathml/nsMathMLmactionFrame.h
+++ b/layout/mathml/nsMathMLmactionFrame.h
@@ -83,6 +83,11 @@ public:
          const nsHTMLReflowState& aReflowState,
          nsReflowStatus&          aStatus);
 
+  NS_IMETHOD
+  AttributeChanged(PRInt32  aNameSpaceID,
+                   nsIAtom* aAttribute,
+                   PRInt32  aModType);
+
 private:
   void MouseClick();
   void MouseOver();