diff --git a/builtin/show-index.c b/builtin/show-index.c
index 8106b03a6b..0e0b9fb95b 100644
--- a/builtin/show-index.c
+++ b/builtin/show-index.c
@@ -71,9 +71,11 @@ int cmd_show_index(int argc, const char **argv, const char *prefix)
 			uint32_t off;
 		} *entries;
 		ALLOC_ARRAY(entries, nr);
-		for (i = 0; i < nr; i++)
+		for (i = 0; i < nr; i++) {
 			if (fread(entries[i].oid.hash, hashsz, 1, stdin) != 1)
 				die("unable to read sha1 %u/%u", i, nr);
+			entries[i].oid.algo = hash_algo_by_ptr(the_hash_algo);
+		}
 		for (i = 0; i < nr; i++)
 			if (fread(&entries[i].crc, 4, 1, stdin) != 1)
 				die("unable to read crc %u/%u", i, nr);