diff --git a/armsrc/iso14443a.c b/armsrc/iso14443a.c
index d5dd05ca1..fe284352d 100644
--- a/armsrc/iso14443a.c
+++ b/armsrc/iso14443a.c
@@ -1861,10 +1861,9 @@ void ReaderIso14443a(UsbCommand *c)
 		if(param & ISO14A_APPEND_CRC) {
 			AppendCrc14443a(cmd,len);
 			len += 2;
-			lenbits += 16;
+			if (lenbits) lenbits += 16;
 		}
 		if(lenbits>0) {
-
 			ReaderTransmitBitsPar(cmd,lenbits,GetParity(cmd,lenbits/8), NULL);
 		} else {
 			ReaderTransmit(cmd,len, NULL);