diff --git a/xrd.py b/xrd.py
index eeca5a0..dc836c9 100644
--- a/xrd.py
+++ b/xrd.py
@@ -131,7 +131,7 @@ def process_command(tef: AutoFMAM, data: bytes, state: State, conn: socket.socke
             if freq <= 27000: tef.modulation = Modulation.AM
             elif freq >= 64000: tef.modulation = Modulation.FM
             else:
-                out += f"!Invalid frequency".encode()
+                out += f"!Invalid frequency\n".encode()
                 continue
 
             match tef.modulation: