--- a/content/html/content/src/nsHTMLFieldSetElement.cpp
+++ b/content/html/content/src/nsHTMLFieldSetElement.cpp
@@ -188,17 +188,17 @@ nsHTMLFieldSetElement::InsertChildAt(nsI
 
   if (aChild->IsHTML(nsGkAtoms::legend)) {
     if (!mFirstLegend) {
       mFirstLegend = aChild;
       // We do not want to notify the first time mFirstElement is set.
     } else {
       // If mFirstLegend is before aIndex, we do not change it.
       // Otherwise, mFirstLegend is now aChild.
-      if (PRInt32(aIndex) <= IndexOf(mFirstLegend)) {
+      if (aIndex <= IndexOf(mFirstLegend)) {
         mFirstLegend = aChild;
         firstLegendHasChanged = true;
       }
     }
   }
 
   nsresult rv = nsGenericHTMLFormElement::InsertChildAt(aChild, aIndex, aNotify);
   NS_ENSURE_SUCCESS(rv, rv);