diff --git a/zulip_bots/zulip_bots/bots/virtual_fs/test_virtual_fs.py b/zulip_bots/zulip_bots/bots/virtual_fs/test_virtual_fs.py
index ec85cd6..72c2aab 100755
--- a/zulip_bots/zulip_bots/bots/virtual_fs/test_virtual_fs.py
+++ b/zulip_bots/zulip_bots/bots/virtual_fs/test_virtual_fs.py
@@ -36,7 +36,11 @@ class TestVirtualFsBot(BotTestCase):
             ("", self.help_txt),
             ("pwd", "foo@example.com:\n/"),
             ("cd /home", "foo@example.com:\nERROR: invalid path"),
+            ("mkdir etc", "foo@example.com:\ndirectory created"),
             ("mkdir home", "foo@example.com:\ndirectory created"),
             ("cd /home", "foo@example.com:\nCurrent path: /home/"),
+            ("mkdir steve", "foo@example.com:\ndirectory created"),
+            ("rmdir /home", "foo@example.com:\nremoved"),
+            ("ls", "foo@example.com:\nERROR: file does not exist"),
         ]
         self.verify_dialog(expected)
diff --git a/zulip_bots/zulip_bots/bots/virtual_fs/virtual_fs.py b/zulip_bots/zulip_bots/bots/virtual_fs/virtual_fs.py
index 0e72a4d..35fe4fd 100644
--- a/zulip_bots/zulip_bots/bots/virtual_fs/virtual_fs.py
+++ b/zulip_bots/zulip_bots/bots/virtual_fs/virtual_fs.py
@@ -252,7 +252,7 @@ def fs_rmdir(fs: Dict[str, Any], user: str, fn: str) -> Tuple[Dict[str, Any], An
     new_fs.pop(path)
     directory = get_directory(path)
     new_fs[directory]['fns'].remove(path)
-    for sub_path in new_fs.keys():
+    for sub_path in list(new_fs.keys()):
         if sub_path.startswith(path+'/'):
             new_fs.pop(sub_path)
     msg = 'removed'