diff --git a/cps/server.py b/cps/server.py
index 14ab0c37..1a25a72e 100644
--- a/cps/server.py
+++ b/cps/server.py
@@ -266,7 +266,7 @@ class WebServer(object):
         if os.environ.get('FLASK_DEBUG'):
             subprocess.run(args, close_fds=True)  # nosec
         else:
-            subprocess.Popen(args, close_fds=True)  # nosec
+            subprocess.run(args, close_fds=True)  # nosec
         return True
 
     @staticmethod