1 files changed, 1 insertions, 0 deletions
diff --git a/pack.c b/pack.c
index b22a8348b2..8e58364024 100644
--- a/pack.c
+++ b/pack.c
@@ -1001,6 +1001,7 @@ pack_pack(ary, fmt)
     if (associates) {
 	rb_str_associate(res, associates);
     }
+    OBJ_INFECT(res, fmt);
     return res;
 }