--- a/browser/confvars.sh
+++ b/browser/confvars.sh
@@ -51,10 +51,13 @@ MOZ_APP_STATIC_INI=1
 MOZ_WEBGL_CONFORMANT=1
 # Enable navigator.mozPay
 MOZ_PAY=1
 # Enable activities. These are used for FxOS developers currently.
 MOZ_ACTIVITIES=1
 MOZ_JSDOWNLOADS=1
 MOZ_RUST_MP4PARSE=1
 
+# Enable checking that add-ons are signed by the trusted root
+MOZ_ADDON_SIGNING=1
+
 # Include the DevTools client, not just the server (which is the default)
 MOZ_DEVTOOLS=all

--- a/mobile/android/confvars.sh
+++ b/mobile/android/confvars.sh
@@ -59,8 +59,11 @@ fi
 # Mark as WebGL conformant
 MOZ_WEBGL_CONFORMANT=1
 
 # Build and package the install bouncer APK by default.
 MOZ_ANDROID_PACKAGE_INSTALL_BOUNCER=1
 
 # Use the low-memory GC tuning.
 export JS_GC_SMALL_CHUNK_SIZE=1
+
+# Enable checking that add-ons are signed by the trusted root
+MOZ_ADDON_SIGNING=1