diff --git a/scripts/mkvenv.py b/scripts/mkvenv.py
index fe070c2e7..eecb0d792 100755
--- a/scripts/mkvenv.py
+++ b/scripts/mkvenv.py
@@ -118,7 +118,7 @@ def _version_key(v):
     try:
         return tuple(int(v) for c in v.split('.'))
     except ValueError:
-        return 999
+        return (999,)
 
 
 def pyqt_versions() -> List[str]: