diff --git a/test/runner/lib/executor.py b/test/runner/lib/executor.py
index 58de39316e2..87884b8ce20 100644
--- a/test/runner/lib/executor.py
+++ b/test/runner/lib/executor.py
@@ -1332,7 +1332,7 @@ def command_units(args):
 
     version_commands = []
 
-    available_versions = get_available_python_versions(SUPPORTED_PYTHON_VERSIONS)
+    available_versions = get_available_python_versions(list(SUPPORTED_PYTHON_VERSIONS))
 
     for version in SUPPORTED_PYTHON_VERSIONS:
         # run all versions unless version given, in which case run only that version