diff --git a/config.js b/config.js
index 10850d24e..74bcdda35 100644
--- a/config.js
+++ b/config.js
@@ -40,7 +40,7 @@ var config = { // eslint-disable-line no-unused-vars
     // up to and including 41. On Firefox 42 and higher, we will run without the
     // extension.
     // If set to -1, an extension will be required for all versions of Firefox.
-    desktopSharingFirefoxMaxVersionExtRequired: -1,
+    desktopSharingFirefoxMaxVersionExtRequired: 51,
     // The URL to the Firefox extension for desktop sharing.
     desktopSharingFirefoxExtensionURL: null,