--- a/toolkit/xre/nsUpdateDriver.cpp
+++ b/toolkit/xre/nsUpdateDriver.cpp
@@ -120,22 +120,21 @@ GetCurrentWorkingDir(char *buf, size_t s
 {
   // Cannot use NS_GetSpecialDirectory because XPCOM is not yet initialized.
   // This code is duplicated from xpcom/io/SpecialSystemDirectory.cpp:
 
 #if defined(XP_OS2)
   if (DosQueryPathInfo( ".", FIL_QUERYFULLNAME, buf, size))
     return NS_ERROR_FAILURE;
 #elif defined(XP_WIN)
-  wchar_t *wpath = _wgetcwd(NULL, size);
-  if (!wpath)
+  wchar_t wpath[MAX_PATH];
+  if (!_wgetcwd(wpath, size))
     return NS_ERROR_FAILURE;
   NS_ConvertUTF16toUTF8 path(wpath);
   strncpy(buf, path.get(), size);
-  free(wpath);
 #else
   if(!getcwd(buf, size))
     return NS_ERROR_FAILURE;
 #endif
   return NS_OK;
 }
 
 #if defined(XP_MACOSX)