--- a/browser/app/profile/firefox.js
+++ b/browser/app/profile/firefox.js
@@ -1512,16 +1512,21 @@ pref("browser.tabs.crashReporting.includ
 pref("browser.tabs.crashReporting.requestEmail", false);
 pref("browser.tabs.crashReporting.emailMe", false);
 pref("browser.tabs.crashReporting.email", "");
 
 // Enable e10s add-on interposition by default.
 pref("extensions.interposition.enabled", true);
 pref("extensions.interposition.prefetching", true);
 
+// But don't allow non-MPC extensions by default on Nightly
+#if defined(NIGHTLY_BUILD)
+pref("extensions.allow-non-mpc-extensions", false);
+#endif
+
 // Enable blocking of e10s and e10s-multi for add-on users on beta/release.
 #ifdef RELEASE_OR_BETA
 pref("extensions.e10sBlocksEnabling", true);
 pref("extensions.e10sMultiBlocksEnabling", true);
 #endif
 
 // How often to check for CPOW timeouts. CPOWs are only timed out by
 // the hang monitor.

--- a/toolkit/mozapps/extensions/internal/XPIProvider.jsm
+++ b/toolkit/mozapps/extensions/internal/XPIProvider.jsm
@@ -185,17 +185,17 @@ const XPI_PERMISSION                  = 
 
 const RDFURI_INSTALL_MANIFEST_ROOT    = "urn:mozilla:install-manifest";
 const PREFIX_NS_EM                    = "http://www.mozilla.org/2004/em-rdf#";
 
 const TOOLKIT_ID                      = "toolkit@mozilla.org";
 
 const XPI_SIGNATURE_CHECK_PERIOD      = 24 * 60 * 60;
 
-XPCOMUtils.defineConstant(this, "DB_SCHEMA", 19);
+XPCOMUtils.defineConstant(this, "DB_SCHEMA", 20);
 
 XPCOMUtils.defineLazyPreferenceGetter(this, "ALLOW_NON_MPC", PREF_ALLOW_NON_MPC);
 
 const NOTIFICATION_TOOLBOXPROCESS_LOADED      = "ToolboxProcessLoaded";
 
 // Properties that exist in the install manifest
 const PROP_METADATA      = ["id", "version", "type", "internalName", "updateURL",
                             "updateKey", "optionsURL", "optionsType", "aboutURL",