--- a/browser/components/enterprisepolicies/Policies.jsm
+++ b/browser/components/enterprisepolicies/Policies.jsm
@@ -505,16 +505,19 @@ var Policies = {
 
   "InstallAddons": {
     onBeforeUIStartup(manager, param) {
       if ("Allow" in param) {
         addAllowDenyPermissions("install", param.Allow, null);
       }
       if ("Default" in param) {
         setAndLockPref("xpinstall.enabled", param.Default);
+        if (!param.Default) {
+          manager.disallowFeature("about:debugging");
+        }
       }
     }
   },
 
   "NoDefaultBookmarks": {
     onProfileAfterChange(manager, param) {
       if (param) {
         manager.disallowFeature("defaultBookmarks");