diff --git a/content/html/document/src/nsHTMLDocument.cpp b/content/html/document/src/nsHTMLDocument.cpp
index 0bd94fa0bb3..6bcc88c8dee 100644
--- a/content/html/document/src/nsHTMLDocument.cpp
+++ b/content/html/document/src/nsHTMLDocument.cpp
@@ -1221,24 +1221,19 @@ nsHTMLDocument::InternalAddStyleSheet(nsIStyleSheet* aSheet, PRUint32 aFlags)
 {
   if (aSheet == mAttrStyleSheet) {  // always first
     NS_ASSERTION(mStyleSheets.Count() == 0 ||
-                 mAttrStyleSheet !=
-                   NS_STATIC_CAST(nsIStyleSheet*, mStyleSheets[0]),
+                 mAttrStyleSheet != mStyleSheets[0],
                  "Adding attr sheet twice!");
     mStyleSheets.InsertObjectAt(aSheet, 0);
   }
   else if (aSheet == mStyleAttrStyleSheet) {  // always last
     NS_ASSERTION(mStyleSheets.Count() == 0 ||
-                 NS_STATIC_CAST(nsIStyleSheet*,
-                                mStyleSheets[mStyleSheets.Count() - 1]) !=
-                   mStyleAttrStyleSheet,
+                 mStyleSheets[mStyleSheets.Count() - 1] != mStyleAttrStyleSheet,
                  "Adding style attr sheet twice!");
     mStyleSheets.AppendObject(aSheet);
   }
   else {
     PRInt32 count = mStyleSheets.Count();
-    if (count != 0 &&
-        mStyleAttrStyleSheet ==
-          NS_STATIC_CAST(nsIStyleSheet*, mStyleSheets[count - 1])) {
+    if (count != 0 && mStyleAttrStyleSheet == mStyleSheets[count - 1]) {
       // keep attr sheet last
       mStyleSheets.InsertObjectAt(aSheet, count - 1);
     }
@@ -1287,9 +1282,7 @@ PRInt32
 nsHTMLDocument::InternalGetNumberOfStyleSheets()
 {
   PRInt32 count = mStyleSheets.Count();
-  if (count != 0 && 
-      mStyleAttrStyleSheet == 
-          NS_STATIC_CAST(nsIStyleSheet*, mStyleSheets[count - 1]))
+  if (count != 0 && mStyleAttrStyleSheet == mStyleSheets[count - 1])
     --count;
   --count; // for the attr sheet
   NS_ASSERTION(count >= 0, "Why did we end up with a negative count?");