--- a/toolkit/xre/nsAppRunner.cpp
+++ b/toolkit/xre/nsAppRunner.cpp
@@ -4359,18 +4359,19 @@ XREMain::XRE_mainRun()
   nsCOMPtr<nsIAppStartup> appStartup
     (do_GetService(NS_APPSTARTUP_CONTRACTID));
   NS_ENSURE_TRUE(appStartup, NS_ERROR_FAILURE);
 
 
 #ifdef XP_WIN
   if (!PR_GetEnv("XRE_NO_DLL_READAHEAD"))
   {
-    PR_CreateThread(PR_USER_THREAD, ReadAheadDlls_ThreadStart, 0, PR_PRIORITY_LOW,
-                    PR_GLOBAL_THREAD, PR_UNJOINABLE_THREAD, 0);
+    PR_CreateThread(PR_USER_THREAD, ReadAheadDlls_ThreadStart, 0,
+                    PR_PRIORITY_NORMAL, PR_GLOBAL_THREAD,
+                    PR_UNJOINABLE_THREAD, 0);
   }
 #endif
 
   if (gDoMigration) {
     nsCOMPtr<nsIFile> file;
     mDirProvider.GetAppDir()->Clone(getter_AddRefs(file));
     file->AppendNative(NS_LITERAL_CSTRING("override.ini"));
     nsINIParser parser;