diff --git a/chain.c b/chain.c
index 4947a3e..d8c1eae 100644
--- a/chain.c
+++ b/chain.c
@@ -28,6 +28,7 @@ mm128_t *mm_chain_dp(int max_dist_x, int max_dist_y, int bw, int max_skip, int m
 	mm128_t *b, *w;
 
 	if (_u) *_u = 0, *n_u_ = 0;
+	if (n == 0 || a == 0) return 0;
 	f = (int32_t*)kmalloc(km, n * 4);
 	p = (int32_t*)kmalloc(km, n * 4);
 	t = (int32_t*)kmalloc(km, n * 4);
diff --git a/hit.c b/hit.c
index 92aa6b7..f43b0d6 100644
--- a/hit.c
+++ b/hit.c
@@ -449,6 +449,7 @@ void mm_set_mapq(void *km, int n_regs, mm_reg1_t *regs, int min_chain_sc, int ma
 	int64_t sum_sc = 0;
 	float uniq_ratio;
 	int i;
+	if (n_regs == 0) return;
 	for (i = 0; i < n_regs; ++i)
 		if (regs[i].parent == regs[i].id)
 			sum_sc += regs[i].score;
diff --git a/main.c b/main.c
index 798f6d7..970884e 100644
--- a/main.c
+++ b/main.c
@@ -6,7 +6,7 @@
 #include "mmpriv.h"
 #include "ketopt.h"
 
-#define MM_VERSION "2.15-r913-dirty"
+#define MM_VERSION "2.15-r914-dirty"
 
 #ifdef __linux__
 #include <sys/resource.h>