--- a/modules/libpref/Preferences.cpp
+++ b/modules/libpref/Preferences.cpp
@@ -5401,18 +5401,16 @@ static mozilla::Module::CIDEntry kPrefCI
   { &kRelativeFilePrefCID, false, nullptr, nsRelativeFilePrefConstructor },
   { nullptr }
 };
 
 static mozilla::Module::ContractIDEntry kPrefContracts[] = {
   { NS_PREFSERVICE_CONTRACTID, &kPrefServiceCID },
   { NS_PREFLOCALIZEDSTRING_CONTRACTID, &kPrefLocalizedStringCID },
   { NS_RELATIVEFILEPREF_CONTRACTID, &kRelativeFilePrefCID },
-  // compatibility for extension that uses old service
-  { "@mozilla.org/preferences;1", &kPrefServiceCID },
   { nullptr }
 };
 
 static void
 UnloadPrefsModule()
 {
   Preferences::Shutdown();
 }