1 files changed, 2 insertions, 1 deletions
diff --git a/test/big.c b/test/big.c
index 5a70c26..831a2ed 100644
--- a/test/big.c
+++ b/test/big.c
@@ -435,7 +435,8 @@ writer (char* filename, hid_t fapl, fsizes_t testsize, int wrt_n)
     hs_size[0] = WRT_SIZE;
     if ((mem_space = H5Screate_simple (1, hs_size, hs_size)) < 0) goto error;
     for (i=0; i<wrt_n; i++) {
-        hs_start[0] = randll (size2[0], i);
+	/* start position must be at least hs_size from the end */
+        hs_start[0] = randll (size2[0]-hs_size[0], i);
         HDfprintf (out, "#%03d 0x%016Hx\n", i, hs_start[0]);
         if (H5Sselect_hyperslab (space2, H5S_SELECT_SET, hs_start, NULL,
                 hs_size, NULL) < 0) goto error;