diff --git a/main.c b/main.c
index 19359f6..1421959 100644
--- a/main.c
+++ b/main.c
@@ -6,7 +6,7 @@
 #include "mmpriv.h"
 #include "ketopt.h"
 
-#define MM_VERSION "2.15-r908-dirty"
+#define MM_VERSION "2.15-r910-dirty"
 
 #ifdef __linux__
 #include <sys/resource.h>
diff --git a/splitidx.c b/splitidx.c
index 6d12071..478a76e 100644
--- a/splitidx.c
+++ b/splitidx.c
@@ -11,8 +11,11 @@ FILE *mm_split_init(const char *prefix, const mm_idx_t *mi)
 	uint32_t i, k = mi->k;
 	fn = (char*)calloc(strlen(prefix) + 10, 1);
 	sprintf(fn, "%s.%.4d.tmp", prefix, mi->index);
-	fp = fopen(fn, "wb");
-	assert(fp);
+	if ((fp = fopen(fn, "wb")) == NULL) {
+		if (mm_verbose >= 1)
+			fprintf(stderr, "[E::%s] failed to create file '%s'\n", __func__, fn);
+		exit(1);
+	}
 	mm_err_fwrite(&k, 4, 1, fp);
 	mm_err_fwrite(&mi->n_seq, 4, 1, fp);
 	for (i = 0; i < mi->n_seq; ++i) {