diff --git a/mysql-test/r/ps_11bugs.result b/mysql-test/r/ps_11bugs.result
index c0d7fe502af..c849c25d646 100644
--- a/mysql-test/r/ps_11bugs.result
+++ b/mysql-test/r/ps_11bugs.result
@@ -116,3 +116,17 @@ execute st_1676 using @arg0, @arg1, @arg2;
 cola	colb	cold
 aaaa	yyyy	R
 drop table t1, t2;
+create table t1 (a int primary key);
+insert into t1 values (1);
+explain select * from t1 where 3 in (select (1+1) union select 1);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
+2	DEPENDENT SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+3	DEPENDENT UNION	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+NULL	UNION RESULT	<union2,3>	ALL	NULL	NULL	NULL	NULL	NULL	
+select * from t1 where 3 in (select (1+1) union select 1);
+a
+prepare st_18492 from 'select * from t1 where 3 in (select (1+1) union select 1)';
+execute st_18492;
+a
+drop table t1;
diff --git a/mysql-test/r/subselect.result b/mysql-test/r/subselect.result
index 500aa4b1728..7925715a8b7 100644
--- a/mysql-test/r/subselect.result
+++ b/mysql-test/r/subselect.result
@@ -734,7 +734,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 3	DEPENDENT UNION	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
 NULL	UNION RESULT	<union2,3>	ALL	NULL	NULL	NULL	NULL	NULL	
 Warnings:
-Note	1003	select test.t2.id AS `id` from test.t2 where <in_optimizer>(test.t2.id,<exists>(select 1 AS `Not_used` having (<cache>(test.t2.id) = <null_helper>(1)) union select 1 AS `Not_used` having (<cache>(test.t2.id) = <null_helper>(3))))
+Note	1003	select test.t2.id AS `id` from test.t2 where <in_optimizer>(test.t2.id,<exists>(select 1 AS `1` having (<cache>(test.t2.id) = <ref_null_helper>(1)) union select 3 AS `3` having (<cache>(test.t2.id) = <ref_null_helper>(3))))
 SELECT * FROM t2 WHERE id IN (SELECT 5 UNION SELECT 3);
 id
 SELECT * FROM t2 WHERE id IN (SELECT 5 UNION SELECT 2);
diff --git a/mysql-test/t/ps_11bugs.test b/mysql-test/t/ps_11bugs.test
index e214afeaaf3..ff1c87f3bd8 100644
--- a/mysql-test/t/ps_11bugs.test
+++ b/mysql-test/t/ps_11bugs.test
@@ -130,3 +130,17 @@ drop table t1, t2;
 # end of bug#1676
 
 # End of 4.1 tests
+
+# bug#18492: mysqld reports ER_ILLEGAL_REFERENCE in --ps-protocol
+
+create table t1 (a int primary key);
+insert into t1 values (1);
+
+explain select * from t1 where 3 in (select (1+1) union select 1);
+
+select * from t1 where 3 in (select (1+1) union select 1);
+
+prepare st_18492 from 'select * from t1 where 3 in (select (1+1) union select 1)';
+execute st_18492;
+
+drop table t1;
diff --git a/sql/item.cc b/sql/item.cc
index 5964ed388c6..7c9f6ec77fb 100644
--- a/sql/item.cc
+++ b/sql/item.cc
@@ -2716,14 +2716,6 @@ void Item_ref_null_helper::print(String *str)
 }
 
 
-void Item_null_helper::print(String *str)
-{
-  str->append("<null_helper>(", 14);
-  store->print(str);
-  str->append(')');
-}
-
-
 bool Item_default_value::eq(const Item *item, bool binary_cmp) const
 {
   return item->type() == DEFAULT_VALUE_ITEM && 
diff --git a/sql/item.h b/sql/item.h
index 1d01ce0d3f3..66da7ad4e74 100644
--- a/sql/item.h
+++ b/sql/item.h
@@ -1045,19 +1045,6 @@ public:
   }
 };
 
-class Item_null_helper :public Item_ref_null_helper
-{
-  Item *store;
-public:
-  Item_null_helper(Item_in_subselect* master, Item *item,
-		   const char *table_name_par, const char *field_name_par)
-    :Item_ref_null_helper(master, &item, table_name_par, field_name_par),
-     store(item)
-    { ref= &store; }
-  void print(String *str);
-};
-
-
 /*
   The following class is used to optimize comparing of date and bigint columns
   We need to save the original item ('ref') to be able to call
diff --git a/sql/item_subselect.cc b/sql/item_subselect.cc
index c8405a9f8f4..8241a8e0402 100644
--- a/sql/item_subselect.cc
+++ b/sql/item_subselect.cc
@@ -822,13 +822,13 @@ Item_in_subselect::single_value_transformer(JOIN *join,
   }
   else
   {
-    select_lex->item_list.empty();
-    select_lex->item_list.push_back(new Item_int("Not_used",
-						 (longlong) 1, 21));
-    select_lex->ref_pointer_array[0]= select_lex->item_list.head();
     if (select_lex->table_list.elements)
     {
       Item *having= item, *orig_item= item;
+      select_lex->item_list.empty();
+      select_lex->item_list.push_back(new Item_int("Not_used",
+                                                   (longlong) 1, 21));
+      select_lex->ref_pointer_array[0]= select_lex->item_list.head();
       item= func->create(expr, item);
       if (!abort_on_null && orig_item->maybe_null)
       {
@@ -875,9 +875,11 @@ Item_in_subselect::single_value_transformer(JOIN *join,
 	select_lex->having=
 	  join->having=
 	  func->create(expr,
-		       new Item_null_helper(this, item,
-					    (char *)"<no matter>",
-					    (char *)"<result>"));
+                       new Item_ref_null_helper(this,
+                                            select_lex->ref_pointer_array,
+                                            (char *)"<no matter>",
+                                            (char *)"<result>"));
+
 	select_lex->having_fix_field= 1;
 	if (join->having->fix_fields(thd, join->tables_list,
 				     0))