diff --git a/manifest.sh b/manifest.sh
new file mode 100644
index 0000000..193ac5b
--- /dev/null
+++ b/manifest.sh
@@ -0,0 +1,10 @@
+#!/bin/bash
+SRC=src/
+if [[ $1 == "2" ]]; then
+  mv=2
+  min=128
+else
+  mv=3
+  min=666
+fi
+sed -i -re 's/("manifest_version":\s*)[0-9]/\1'$mv'/' -e 's/("strict_min_version":\s*")[0-9]+/\1'$min'/' "$SRC/manifest.json"
\ No newline at end of file
diff --git a/src/manifest.json b/src/manifest.json
index 18ac5c9..10e910c 100644
--- a/src/manifest.json
+++ b/src/manifest.json
@@ -5,7 +5,8 @@
   "browser_specific_settings": {
     "gecko": {
       "id":  "{73a6fe31-595d-460b-a920-fcc0f8843232}",
-      "strict_min_version": "115.0"
+      "strict_min_version": "666.0",
+      "strict_max_version": "665.0"
     },
     "gecko_android": {}
   },