diff --git a/ramalama/cli.py b/ramalama/cli.py
index f84c39e8..6c6af803 100644
--- a/ramalama/cli.py
+++ b/ramalama/cli.py
@@ -381,7 +381,7 @@ def containers_parser(subparsers):
 
 def _list_containers(args):
     conman = args.engine
-    if conman == "":
+    if conman == "" or conman == None:
         raise ValueError("no container manager (Podman, Docker) found")
 
     conman_args = [conman, "ps", "-a", "--filter", "label=RAMALAMA"]