diff --git a/lib/ansible/modules/network/aci/aci_bd_subnet.py b/lib/ansible/modules/network/aci/aci_bd_subnet.py
index 5117d6325c..3f63f09d82 100644
--- a/lib/ansible/modules/network/aci/aci_bd_subnet.py
+++ b/lib/ansible/modules/network/aci/aci_bd_subnet.py
@@ -358,10 +358,11 @@ def main():
     route_profile = module.params['route_profile']
     route_profile_l3_out = module.params['route_profile_l3_out']
     scope = module.params['scope']
-    if 'private' in scope and 'public' in scope:
-        module.fail_json(msg="Parameter 'scope' cannot be both 'private' and 'public', got: %s" % scope)
-    else:
-        scope = ','.join(sorted(scope))
+    if scope is not None:
+        if 'private' in scope and 'public' in scope:
+            module.fail_json(msg="Parameter 'scope' cannot be both 'private' and 'public', got: %s" % scope)
+        else:
+            scope = ','.join(sorted(scope))
     state = module.params['state']
     subnet_control = module.params['subnet_control']
     if subnet_control: