diff --git a/ChangeLog b/ChangeLog
index 87b5f1deab..a9f0af3cfc 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Sun Aug 14 22:35:40 2016  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* id_table.c (hash_table_extend): should not shrink the table than
+	  the previous capacity.  [ruby-core:76534] [Bug #12614]
+
 Sun Aug 14 18:51:24 2016  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* gems/bundled_gems: add gemified tk 0.1.0.
diff --git a/id_table.c b/id_table.c
index 1d1d684745..f0f37cc913 100644
--- a/id_table.c
+++ b/id_table.c
@@ -1311,6 +1311,9 @@ hash_table_extend(struct hash_id_table* tbl)
 	int i;
 	item_t* old;
 	struct hash_id_table tmp_tbl = {0, 0, 0};
+	if (new_cap < tbl->capa) {
+	    new_cap = round_capa(tbl->used + (tbl->used >> 1));
+	}
 	tmp_tbl.capa = new_cap;
 	tmp_tbl.items = ZALLOC_N(item_t, new_cap);
 	for (i = 0; i < tbl->capa; i++) {