diff --git a/xrd.py b/xrd.py
index edd46d1..2f61390 100644
--- a/xrd.py
+++ b/xrd.py
@@ -183,9 +183,9 @@ def send_signal_status(tef: TEF6686, conn: socket.socket, state: State):
     data = b"S"
 
     stereo_pilot, _ = d if (d := tef.FM_Get_Signal_Status()) else (None, None)
-    if state.forced_mono: data += b"M"
-    elif stereo_pilot: data += b"s"
-    else: data += b"m"
+    letter = b"s" if stereo_pilot else b"m"
+    if state.forced_mono: letter = letter.upper()
+    data += letter
 
     if not state.last_bw_extend and level > 38 and usn < 7:
         tef.FM_Set_Bandwidth_Options(400)