diff --git a/extensions/transformiix/source/base/TxString.h b/extensions/transformiix/source/base/TxString.h
index d5c50a612329..b26daefea9f8 100644
--- a/extensions/transformiix/source/base/TxString.h
+++ b/extensions/transformiix/source/base/TxString.h
@@ -174,16 +174,6 @@ public:
      */
     String& operator = (const String& aSource);
 #else
-    /*
-     * Return a reference to this string's nsString.
-     */
-    operator nsAFlatString&();
-
-    /*
-     * Return a const reference to this string's nsString.
-     */
-    operator const nsAFlatString&() const;
-
     /*
      * Return a reference to this string's nsString.
      */
diff --git a/extensions/transformiix/source/base/txMozillaString.h b/extensions/transformiix/source/base/txMozillaString.h
index 36aab990767e..ef412b5ebd08 100644
--- a/extensions/transformiix/source/base/txMozillaString.h
+++ b/extensions/transformiix/source/base/txMozillaString.h
@@ -208,16 +208,6 @@ inline void String::toUpperCase()
   ToUpperCase(mString);
 }
 
-inline String::operator nsAFlatString&()
-{
-  return mString;
-}
-
-inline String::operator const nsAFlatString&() const
-{
-  return mString;
-}
-
 inline String::operator nsAString&()
 {
   return mString;