diff --git a/platform/chromium/manifest.json b/platform/chromium/manifest.json
index 2481512..b9d93db 100644
--- a/platform/chromium/manifest.json
+++ b/platform/chromium/manifest.json
@@ -2,7 +2,7 @@
     "manifest_version": 2,
     "name": "uMatrix",
     "short_name": "uMatrix",
-    "version": "0.9.9",
+    "version": "0.9.9.3",
     "description": "__MSG_extShortDesc__",
     "icons": {
         "16": "img/icon_16.png",
diff --git a/tools/make-firefox-meta.py b/tools/make-firefox-meta.py
index 36550a1..8aa2f4e 100644
--- a/tools/make-firefox-meta.py
+++ b/tools/make-firefox-meta.py
@@ -2,6 +2,7 @@
 
 import os
 import json
+import re
 import sys
 from io import open
 from shutil import rmtree
@@ -76,8 +77,15 @@ with open(chromium_manifest, encoding='utf-8') as m:
 
 # https://developer.mozilla.org/en-US/Add-ons/AMO/Policy/Maintenance#How_do_I_submit_a_Beta_add-on.3F
 # "To create a beta channel [...] '(a|alpha|b|beta|pre|rc)\d*$' "
-if sys.argv[2]:
-    manifest['version'] += sys.argv[2]
+
+match = re.search('^(\d+\.\d+\.\d+)(\.\d+)$', manifest['version'])
+if match:
+    buildtype = int(match.group(2)[1:])
+    if buildtype < 100:
+        builttype = 'b' + str(buildtype)
+    else:
+        builttype = 'rc' + str(buildtype - 100)
+    manifest['version'] = match.group(1) + builttype
 
 manifest['homepage'] = 'https://github.com/gorhill/uMatrix'
 manifest['description'] = escape(descriptions['en'])
diff --git a/tools/make-firefox.sh b/tools/make-firefox.sh
index 52a1132..a00f0e1 100755
--- a/tools/make-firefox.sh
+++ b/tools/make-firefox.sh
@@ -29,7 +29,7 @@ cp    platform/firefox/*.xul            $DES/
 cp    LICENSE.txt                       $DES/
 
 echo "*** uMatrix.firefox: Generating meta..."
-python tools/make-firefox-meta.py $DES/ "$2"
+python tools/make-firefox-meta.py $DES/
 
 if [ "$1" = all ]; then
     echo "*** uMatrix.firefox: Creating package..."