diff --git a/bwape.c b/bwape.c
index 92161a5..6752a18 100644
--- a/bwape.c
+++ b/bwape.c
@@ -106,6 +106,11 @@ static int infer_isize(int n_seqs, bwa_seq_t *seqs[2], isize_info_t *ii, double
 	tmp  = (int)(p25 - OUTLIER_BOUND * (p75 - p25) + .499);
 	ii->low = tmp > max_len? tmp : max_len; // ii->low is unsigned
 	ii->high = (int)(p75 + OUTLIER_BOUND * (p75 - p25) + .499);
+	if (ii->low > ii->high) {
+		fprintf(stderr, "[infer_isize] fail to infer insert size: upper bound is smaller than read length\n");
+		free(isizes);
+		return -1;
+	}
 	for (i = 0, x = n = 0; i < tot; ++i)
 		if (isizes[i] >= ii->low && isizes[i] <= ii->high)
 			++n, x += isizes[i];
diff --git a/main.c b/main.c
index 4fa2522..85e41b2 100644
--- a/main.c
+++ b/main.c
@@ -3,7 +3,7 @@
 #include "utils.h"
 
 #ifndef PACKAGE_VERSION
-#define PACKAGE_VERSION "0.7.3-r380-beta"
+#define PACKAGE_VERSION "0.7.3-r381-beta"
 #endif
 
 int bwa_fa2pac(int argc, char *argv[]);