diff --git a/tools/wpt/run.py b/tools/wpt/run.py
index 5761ab89cc98ca..cb396782be0189 100644
--- a/tools/wpt/run.py
+++ b/tools/wpt/run.py
@@ -457,7 +457,8 @@ def log(x):
 
 def run_single(venv, **kwargs):
     from wptrunner import wptrunner
-    return wptrunner.start(**kwargs)
+    wptrunner.start(**kwargs)
+    return
 
 
 def main():