diff --git a/toolkit/xre/nsNativeAppSupportWin.cpp b/toolkit/xre/nsNativeAppSupportWin.cpp
index 4319bd1679..622fa58a7d 100644
--- a/toolkit/xre/nsNativeAppSupportWin.cpp
+++ b/toolkit/xre/nsNativeAppSupportWin.cpp
@@ -505,7 +505,7 @@ struct MessageWindow {
             ::_snwprintf(classNameBuffer,
                          128,   // size of classNameBuffer in PRUnichars
                          L"%s%s",
-                         wwc(NS_ConvertUTF8toUTF16(gAppData->remotingName).get()),
+                         static_cast<const wchar_t*>(NS_ConvertUTF8toUTF16(gAppData->remotingName).get()),
                          L"MessageWindow" );
             mClassName = classNameBuffer;
         }
@@ -668,7 +668,7 @@ nsNativeAppSupportWin::Start( bool *aResult ) {
     ::_snwprintf(reinterpret_cast<wchar_t*>(mMutexName),
                  sizeof mMutexName / sizeof(char16_t), L"%s%s%s",
                  MOZ_MUTEX_NAMESPACE,
-                 wwc(NS_ConvertUTF8toUTF16(gAppData->name).get()),
+                 static_cast<const wchar_t*>(NS_ConvertUTF8toUTF16(gAppData->name).get()),
                  MOZ_STARTUP_MUTEX_NAME );
     Win32Mutex startupLock = Win32Mutex( mMutexName );