Index: firmware/App/Services/SystemCommMessages.c
===================================================================
diff -u -rcc8b9ddb9905161ddb0dc2af6bfbf863408669c8 -rdb5eeea50b6d69b626ce97f0f32377313385a009
--- firmware/App/Services/SystemCommMessages.c	(.../SystemCommMessages.c)	(revision cc8b9ddb9905161ddb0dc2af6bfbf863408669c8)
+++ firmware/App/Services/SystemCommMessages.c	(.../SystemCommMessages.c)	(revision db5eeea50b6d69b626ce97f0f32377313385a009)
@@ -104,7 +104,7 @@
     data[ msgSize++ ] = MESSAGE_SYNC_BYTE;
 
     // set sequence # and ACK bit (unless this is an ACK to a received message)
-    if ( msg.hdr.msgID != MSG_ID_ACK )
+    if ( msg.hdr.msgID != MSG_ID_ACK_MESSAGE_THAT_REQUIRES_ACK )
     {
         // thread protect next sequence # access & increment
         _disable_IRQ();
@@ -177,7 +177,7 @@
     // send ACK back with same seq. #, but w/o ACK bit
     msg.hdr.seqNo = message->hdr.seqNo * -1;
     // ACK messages always have this ID
-    msg.hdr.msgID = MSG_ID_ACK;
+    msg.hdr.msgID = MSG_ID_ACK_MESSAGE_THAT_REQUIRES_ACK;
     // ACK messages always have no payload
     msg.hdr.payloadLen = 0;