diff --git a/package.json b/package.json
index bc1d4b617f66b8b11cbca1c3cdc03b495cd2c538..12ed4ccac57cb571ee5c82d2e44a7ce0e9aa114b 100644
--- a/package.json
+++ b/package.json
@@ -8,6 +8,10 @@
     "homepage": "https://addons.mozilla.org/en-US/firefox/addon/decentraleyes", 
     "name": "decentraleyes",
     "id": "id1-BoFifL9Vbdl2zQ@jetpack", 
+    "engines": {
+        "firefox": ">=21.0", 
+        "fennec": ">=21.0"
+    }, 
     "preferences": [
         {
             "description": "Automatically prepend a notice to retrieved documents to signal local delivery.",