diff --git a/hcxpcapngtool.c b/hcxpcapngtool.c
index b179e551c..ba2c067ae 100644
--- a/hcxpcapngtool.c
+++ b/hcxpcapngtool.c
@@ -5737,16 +5737,20 @@ return;
 static bool processnmeainfile(char *nmeainname)
 {
 static int nlen;
-static int ccs;
-static int ncs;
+static uint8_t ccs;
+static uint8_t ncs;
 static int c;
-uint8_t idx0;
-uint8_t idx1;
 static FILE *fh_nmeain;
 static char *ntok;
 static char *nres;
 const uint8_t hashmap[] =
 {
+0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, // 01234567
 0x08, 0x09, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // 89:;<=>?
 0x00, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f, 0x00, // @ABCDEFG
@@ -5765,9 +5769,7 @@ if((fh_nmeain = fopen(nmeainname, "r")) != NULL)
 		if(nlen < 6) continue;
 		if(linein[0] != '$') continue;
 		if(linein[nlen -3] != '*') continue;
-		idx0 = ((uint8_t)linein[nlen -2] & 0x1F) ^ 0x10;
-		idx1 = ((uint8_t)linein[nlen -1] & 0x1F) ^ 0x10;
-		ncs = (uint8_t)(hashmap[idx0] << 4) | hashmap[idx1];
+		ncs = (hashmap[(uint8_t)linein[nlen -2]] << 4) | hashmap[(uint8_t)linein[nlen -1]];
 		ccs = 0;
 		for(c = 1; c < nlen -3; c++) ccs ^= linein[c];
 		if(ncs != ccs) continue;