diff --git a/preprocess-readme.py b/preprocess-readme.py
index 6b9fb35a6..a9759f6e7 100755
--- a/preprocess-readme.py
+++ b/preprocess-readme.py
@@ -38,7 +38,7 @@ if raw != nraw:
     open('README.asciidoc', 'w').write(nraw)
 
 raw = subprocess.check_output([
-    'kitty', '-c',
+    'kitty', '+runpy',
     'from kitty.key_encoding import *; import json; print(json.dumps(ENCODING))'
 ]).decode('utf-8')
 key_map = json.loads(raw)