diff --git a/main.js b/main.js
index 90e2059..00cb489 100644
--- a/main.js
+++ b/main.js
@@ -544,6 +544,11 @@ client.login("m.login.password", {"user": settings.matrixuser, "password": setti
             return;
         }
 
+        if (event.getContent().body.toLowerCase().replace(/\s/g, "").startsWith("!")) {
+            sendMatrixNotice(event.getRoomId(), "I'm sorry, but my programming forbids me from sending text messages that start with `!`.");
+            return;
+        }
+
         var matches = room.name.match(/SMS_([1-9][0-9]+)(?:_([1-9][0-9]+))?/g);
         console.log(event.getRoomId());
         if (matches == null || (matches.length != 1 && matches.length != 2)) {