diff --git a/DCCEXParser.cpp b/DCCEXParser.cpp
index 967e554..bcdd5d8 100644
--- a/DCCEXParser.cpp
+++ b/DCCEXParser.cpp
@@ -775,6 +775,7 @@ bool DCCEXParser::parseD(Print *stream, int16_t params, int16_t p[])
 	      DCCWaveform::progTrack.setMaxAckPulseDuration(p[2]);
 	      StringFormatter::lcd(0, F("Ack Max=%dus"), p[2]);  //   <D ACK MAX 9000>
 	    } else if (p[1] == HASH_KEYWORD_RETRY) {
+	      if (p[2] >3) p[2]=3;
               DCC::setAckRetry(p[2]);
 	      StringFormatter::lcd(0, F("Ack Retry=%d"), p[2]);  //   <D ACK RETRY 2>
 	    }