diff --git a/bwt.c b/bwt.c
index 43979ac..4ee9ea8 100644
--- a/bwt.c
+++ b/bwt.c
@@ -105,21 +105,20 @@ static inline int __occ_aux(uint64_t y, int c)
 
 bwtint_t bwt_occ(const bwt_t *bwt, bwtint_t k, ubyte_t c)
 {
-	bwtint_t n, l, j;
-	uint32_t *p;
+	bwtint_t n;
+	uint32_t *p, *end;
 
 	if (k == bwt->seq_len) return bwt->L2[c+1] - bwt->L2[c];
 	if (k == (bwtint_t)(-1)) return 0;
-	if (k >= bwt->primary) --k; // because $ is not in bwt
+	k -= (k >= bwt->primary); // because $ is not in bwt
 
 	// retrieve Occ at k/OCC_INTERVAL
 	n = ((bwtint_t*)(p = bwt_occ_intv(bwt, k)))[c];
 	p += sizeof(bwtint_t); // jump to the start of the first BWT cell
 
 	// calculate Occ up to the last k/32
-	j = k >> 5 << 5;
-	for (l = k/OCC_INTERVAL*OCC_INTERVAL; l < j; l += 32, p += 2)
-		n += __occ_aux((uint64_t)p[0]<<32 | p[1], c);
+	end = p + (((k>>5) - ((k&~OCC_INTV_MASK)>>5))<<1);
+	for (; p < end; p += 2) n += __occ_aux((uint64_t)p[0]<<32 | p[1], c);
 
 	// calculate Occ
 	n += __occ_aux(((uint64_t)p[0]<<32 | p[1]) & ~((1ull<<((~k&31)<<1)) - 1), c);
diff --git a/kopen.c b/kopen.c
index 45f2713..8887932 100644
--- a/kopen.c
+++ b/kopen.c
@@ -203,7 +203,7 @@ ftp_open_end:
 static char **cmd2argv(const char *cmd)
 {
 	int i, beg, end, argc;
-	char **argv, *p, *q, *str;
+	char **argv, *str;
 	end = strlen(cmd);
 	for (i = end - 1; i >= 0; --i)
 		if (!isspace(cmd[i])) break;
@@ -217,7 +217,7 @@ static char **cmd2argv(const char *cmd)
 	argv = (char**)calloc(argc + 2, sizeof(void*));
 	argv[0] = str = (char*)calloc(end - beg + 1, 1);
 	strncpy(argv[0], cmd + beg, end - beg);
-	for (i = argc = 1, q = p = str; i < end - beg; ++i)
+	for (i = argc = 1; i < end - beg; ++i)
 		if (isspace(str[i])) str[i] = 0;
 		else if (str[i] && str[i-1] == 0) argv[argc++] = &str[i];
 	return argv;