diff --git a/calendar/manifest.json b/calendar/manifest.json
index c54188e..b2fce3a 100644
--- a/calendar/manifest.json
+++ b/calendar/manifest.json
@@ -6,7 +6,8 @@
   "version": "2.2.0",
   "browser_specific_settings": {
     "gecko": {
-      "id": "ext-calendar-draft@mozilla.kewis.ch"
+      "id": "ext-calendar-draft@mozilla.kewis.ch",
+      "strict_min_version": "128.0"
     }
   },