1 files changed, 2 insertions, 2 deletions

diff --git a/iseq.c b/iseq.c
index 57ff506d0a..20ad68e65e 100644
--- a/iseq.c
+++ b/iseq.c
@@ -208,7 +208,7 @@ iseq_memsize(const rb_iseq_t *iseq)
 
 	cur = compile_data->storage_head;
 	while (cur) {
-	    size += cur->size + sizeof(struct iseq_compile_data_storage);
+	    size += cur->size + offsetof(struct iseq_compile_data_storage, buff);
 	    cur = cur->next;
 	}
     }
@@ -333,7 +333,7 @@ prepare_iseq_build(rb_iseq_t *iseq,
     ISEQ_COMPILE_DATA(iseq)->storage_head = ISEQ_COMPILE_DATA(iseq)->storage_current =
       (struct iseq_compile_data_storage *)
 	ALLOC_N(char, INITIAL_ISEQ_COMPILE_DATA_STORAGE_BUFF_SIZE +
-		sizeof(struct iseq_compile_data_storage));
+		offsetof(struct iseq_compile_data_storage, buff));
 
     RB_OBJ_WRITE(iseq, &ISEQ_COMPILE_DATA(iseq)->catch_table_ary, rb_ary_tmp_new(3));
     ISEQ_COMPILE_DATA(iseq)->storage_head->pos = 0;