diff --git a/tools/make-webext-meta.py b/tools/make-webext-meta.py
index 15f8946e5..b9c7e3551 100644
--- a/tools/make-webext-meta.py
+++ b/tools/make-webext-meta.py
@@ -17,7 +17,7 @@ with open(os.path.join(proj_dir, 'dist', 'version')) as f:
 
 webext_manifest = {}
 webext_manifest_file = os.path.join(build_dir, 'manifest.json')
-with open(webext_manifest_file) as f2:
+with open(webext_manifest_file, encoding='utf-8') as f2:
     webext_manifest = json.load(f2)
 
 webext_manifest['version'] = version
@@ -28,6 +28,6 @@ if match:
     webext_manifest['short_name'] += ' dev build'
     webext_manifest['browser_action']['default_title'] += ' dev build'
 
-with open(webext_manifest_file, 'w') as f2:
+with open(webext_manifest_file, mode='w', encoding='utf-8') as f2:
     json.dump(webext_manifest, f2, indent=2, separators=(',', ': '), sort_keys=True)
     f2.write('\n')
diff --git a/tools/make-webext.sh b/tools/make-webext.sh
index c77b5c0df..cb0ec9fe2 100755
--- a/tools/make-webext.sh
+++ b/tools/make-webext.sh
@@ -2,6 +2,9 @@
 #
 # This script assumes a linux environment
 
+# https://github.com/uBlockOrigin/uBlock-issues/issues/217
+set -e
+
 echo "*** uBlock0.webext: Creating web store package"
 echo "*** uBlock0.webext: Copying files"
 
@@ -45,7 +48,7 @@ cp -R src/web_accessible_resources $DES/
 python3 tools/import-war.py $DES/
 
 echo "*** uBlock0.webext: Generating meta..."
-python tools/make-webext-meta.py $DES/
+python3 tools/make-webext-meta.py $DES/
 
 if [ "$1" = all ]; then
     echo "*** uBlock0.webext: Creating package..."