diff --git a/pyproject.toml b/pyproject.toml
index 873fc43..759527f 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -93,3 +93,4 @@ convention = "pep257"
 [tool.ruff.lint.pylint]
 max-args = 10
 max-nested-blocks = 4
+max-returns = 8
diff --git a/xpartamupp/modbot.py b/xpartamupp/modbot.py
index 0344303..22825fa 100755
--- a/xpartamupp/modbot.py
+++ b/xpartamupp/modbot.py
@@ -45,7 +45,7 @@
 from simplemma.strategies.dictionaries import TrieDictionaryFactory
 from slixmpp import ClientXMPP, Message
 from slixmpp.exceptions import IqError
-from slixmpp.jid import JID
+from slixmpp.jid import JID, InvalidJID
 from slixmpp.plugins.xep_0045 import MUCPresence
 from sqlalchemy import create_engine, func, select, text
 from sqlalchemy.dialects.sqlite.base import SQLiteDialect
@@ -584,7 +584,7 @@ async def _muc_check_profanity(self, msg: Message) -> None:
                 offending_content=msg_body,
             )
 
-    async def _muc_command_message(self, msg: Message) -> None:
+    async def _muc_command_message(self, msg: Message) -> None:  # noqa: C901
         """Process messages in the command MUC room.
 
         Detect commands posted in the command MUC room and act on them.
@@ -626,7 +626,18 @@ async def _muc_command_message(self, msg: Message) -> None:
             await self.send_profanity_term_list(args.lang)
             return
 
-        user = JID(args.user + "@" + self.boundjid.domain)
+        try:
+            user = JID(
+                "".join([c for c in args.user if c.isprintable()]) + "@" + self.boundjid.domain
+            )
+        except InvalidJID:
+            self.send_message(
+                mto=self.command_room,
+                mbody=f'"{args.user}" is an invalid nickname.',
+                mtype="groupchat",
+            )
+            return
+
         moderator = JID(moderator)
         reason = " ".join(args.reason)