diff --git a/lib/nntp/tiny/session.py b/lib/nntp/tiny/session.py
index 2d0bb5b..df6ad50 100644
--- a/lib/nntp/tiny/session.py
+++ b/lib/nntp/tiny/session.py
@@ -361,4 +361,9 @@ class Session():
         if fn is None:
             return self.respond(ResponseCode.NNTP_COMMAND_UNKNOWN)
 
-        return fn(self, *args)
+        try:
+            return fn(self, *args)
+        except TypeError as e:
+            return self.respond(ResponseCode.NNTP_SYNTAX_ERROR)
+        except Exception as e:
+            return self.respond(ResponseCode.NNTP_COMMAND_UNAVAILABLE)