diff --git a/pack-bitmap.c b/pack-bitmap.c
index 074d9ac8f2..4431f9f120 100644
--- a/pack-bitmap.c
+++ b/pack-bitmap.c
@@ -1328,7 +1328,7 @@ void test_bitmap_walk(struct rev_info *revs)
 	if (bitmap_equals(result, tdata.base))
 		fprintf(stderr, "OK!\n");
 	else
-		fprintf(stderr, "Mismatch!\n");
+		die("mismatch in bitmap results");
 
 	free_bitmap_index(bitmap_git);
 }