diff --git a/main.c b/main.c
index 2192ed0..a1f5c5f 100644
--- a/main.c
+++ b/main.c
@@ -6,7 +6,7 @@
 #include "mmpriv.h"
 #include "getopt.h"
 
-#define MM_VERSION "2.2-r411-dirty"
+#define MM_VERSION "2.2-r414-dirty"
 
 #ifdef __linux__
 #include <sys/resource.h>
diff --git a/map.c b/map.c
index 00d88cc..2029203 100644
--- a/map.c
+++ b/map.c
@@ -162,6 +162,9 @@ mm_reg1_t *mm_map(const mm_idx_t *mi, int qlen, const char *seq, int *n_regs, mm
 	mm128_t *a;
 	mm_reg1_t *regs;
 
+	*n_regs = 0;
+	if (qlen == 0) return 0;
+
 	// collect minimizers
 	b->mini.n = 0;
 	mm_sketch(b->km, seq, qlen, mi->w, mi->k, 0, mi->is_hpc, &b->mini);