diff --git a/src/projections/irc/mod.rs b/src/projections/irc/mod.rs
index 6c36716..fc490fd 100644
--- a/src/projections/irc/mod.rs
+++ b/src/projections/irc/mod.rs
@@ -528,7 +528,17 @@ async fn handle_incoming_message(
                             .await?;
                             writer.flush().await?;
                         } else {
-                            // TODO send 502 (not 401) if the user is not the sender
+                            ServerMessage {
+                                tags: vec![],
+                                sender: Some(config.server_name.clone()),
+                                body: ServerMessageBody::N502UsersDontMatch {
+                                    client: user.nickname.clone(),
+                                    message: "Cant change mode for other users".into(),
+                                },
+                            }
+                            .write_async(writer)
+                            .await?;
+                            writer.flush().await?;
                         }
                     }
                     Recipient::Chan(_) => {
diff --git a/src/protos/irc/server.rs b/src/protos/irc/server.rs
index 16b5804..b2efcd4 100644
--- a/src/protos/irc/server.rs
+++ b/src/protos/irc/server.rs
@@ -132,6 +132,10 @@ pub enum ServerMessageBody {
         chan: Chan,
         message: Str,
     },
+    N502UsersDontMatch {
+        client: Str,
+        message: Str,
+    },
 }
 
 impl ServerMessageBody {
@@ -301,6 +305,13 @@ impl ServerMessageBody {
                 writer.write_all(b" :").await?;
                 writer.write_all(message.as_bytes()).await?;
             }
+            ServerMessageBody::N502UsersDontMatch { client, message } => {
+                writer.write_all(b"502 ").await?;
+                writer.write_all(client.as_bytes()).await?;
+                writer.write_all(b" ").await?;
+                writer.write_all(b" :").await?;
+                writer.write_all(message.as_bytes()).await?;
+            }
         }
         Ok(())
     }