diff --git a/bntseq.c b/bntseq.c
index 972837e..540e966 100644
--- a/bntseq.c
+++ b/bntseq.c
@@ -124,7 +124,7 @@ bntseq_t *bns_restore_core(const char *ann_filename, const char* amb_filename, c
 		fscanf(fp, "%lld%d%d", &xx, &n_seqs, &bns->n_holes);
 		l_pac = xx;
 		xassert(l_pac == bns->l_pac && n_seqs == bns->n_seqs, "inconsistent .ann and .amb files.");
-		bns->ambs = (bntamb1_t*)calloc(bns->n_holes, sizeof(bntamb1_t));
+		bns->ambs = bns->n_holes? (bntamb1_t*)calloc(bns->n_holes, sizeof(bntamb1_t)) : 0;
 		for (i = 0; i < bns->n_holes; ++i) {
 			bntamb1_t *p = bns->ambs + i;
 			fscanf(fp, "%lld%d%s", &xx, &p->len, str);
diff --git a/main.c b/main.c
index 7499609..91a62cc 100644
--- a/main.c
+++ b/main.c
@@ -4,7 +4,7 @@
 #include "utils.h"
 
 #ifndef PACKAGE_VERSION
-#define PACKAGE_VERSION "0.7.0-r315"
+#define PACKAGE_VERSION "0.7.0-r316"
 #endif
 
 static int usage()