diff --git a/fastmap.c b/fastmap.c
index 3e8e3b4..69dbcbe 100644
--- a/fastmap.c
+++ b/fastmap.c
@@ -90,9 +90,12 @@ int main_mem(int argc, char *argv[])
 
 	bwa_fill_scmat(opt->a, opt->b, opt->mat);
 	if ((idx = bwa_idx_load(argv[optind], BWA_IDX_ALL)) == 0) return 1; // FIXME: memory leak
-	bwa_print_sam_hdr(idx->bns, rg_line);
 
 	ko = kopen(argv[optind + 1], &fd);
+	if (ko == 0) {
+		if (bwa_verbose >= 1) fprintf(stderr, "[E::%s] fail to open file `%s'.\n", __func__, argv[optind + 1]);
+		return 1;
+	}
 	fp = gzdopen(fd, "r");
 	ks = kseq_init(fp);
 	if (optind + 2 < argc) {
@@ -101,11 +104,16 @@ int main_mem(int argc, char *argv[])
 				fprintf(stderr, "[W::%s] when '-p' is in use, the second query file will be ignored.\n", __func__);
 		} else {
 			ko2 = kopen(argv[optind + 2], &fd2);
+			if (ko2 == 0) {
+				if (bwa_verbose >= 1) fprintf(stderr, "[E::%s] fail to open file `%s'.\n", __func__, argv[optind + 2]);
+				return 1;
+			}
 			fp2 = gzdopen(fd2, "r");
 			ks2 = kseq_init(fp2);
 			opt->flag |= MEM_F_PE;
 		}
 	}
+	bwa_print_sam_hdr(idx->bns, rg_line);
 	while ((seqs = bseq_read(opt->chunk_size * opt->n_threads, &n, ks, ks2)) != 0) {
 		int64_t size = 0;
 		if ((opt->flag & MEM_F_PE) && (n&1) == 1) {
diff --git a/kopen.c b/kopen.c
index 8887932..c0bc975 100644
--- a/kopen.c
+++ b/kopen.c
@@ -292,14 +292,14 @@ void *kopen(const char *fn, int *_fd)
 #else
 			*_fd = open(fn, O_RDONLY);
 #endif
-			if (*_fd) {
+			if (*_fd >= 0) {
 				aux = calloc(1, sizeof(koaux_t));
 				aux->type = KO_FILE;
 				aux->fd = *_fd;
 			}
 		}
 	}
-	*_fd = aux->fd;
+	if (aux) *_fd = aux->fd;
 	return aux;
 }
 
diff --git a/main.c b/main.c
index cb4289c..d40d996 100644
--- a/main.c
+++ b/main.c
@@ -3,7 +3,7 @@
 #include "utils.h"
 
 #ifndef PACKAGE_VERSION
-#define PACKAGE_VERSION "0.7.4-r388-beta"
+#define PACKAGE_VERSION "0.7.4-r389-beta"
 #endif
 
 int bwa_fa2pac(int argc, char *argv[]);
@@ -92,5 +92,5 @@ int main(int argc, char *argv[])
 			fprintf(stderr, " %s", argv[i]);
 		fprintf(stderr, "\n[%s] Real time: %.3f sec; CPU: %.3f sec\n", __func__, realtime() - t_real, cputime());
 	}
-	return 0;
+	return ret;
 }