diff --git a/dom/cache/test/xpcshell/head.js b/dom/cache/test/xpcshell/head.js
index 8cad3ebdcfc8..557ded64ce99 100644
--- a/dom/cache/test/xpcshell/head.js
+++ b/dom/cache/test/xpcshell/head.js
@@ -53,6 +53,7 @@ add_setup(function () {
 });
 
 function enableTesting() {
+  Services.prefs.setBoolPref("dom.caches.testing.enabled", true);
   Services.prefs.setBoolPref("dom.simpleDB.enabled", true);
   Services.prefs.setBoolPref("dom.quotaManager.testing", true);
 }
@@ -60,6 +61,7 @@ function enableTesting() {
 function resetTesting() {
   Services.prefs.clearUserPref("dom.quotaManager.testing");
   Services.prefs.clearUserPref("dom.simpleDB.enabled");
+  Services.prefs.clearUserPref("dom.caches.testing.enabled");
 }
 
 function initStorage() {