diff --git a/mysql-test/r/olap.result b/mysql-test/r/olap.result
index 74b7570ea2a..0300fc1759e 100644
--- a/mysql-test/r/olap.result
+++ b/mysql-test/r/olap.result
@@ -556,3 +556,64 @@ x	a	sum(b)
 2006-07-01	NULL	11
 NULL	NULL	11
 drop table t1;
+CREATE TABLE t1 (a int, b int);
+INSERT INTO t1 
+VALUES (2,10),(3,30),(2,40),(1,10),(2,30),(1,20),(2,10);
+SELECT a, SUM(b) FROM t1 GROUP BY a WITH ROLLUP;
+a	SUM(b)
+1	30
+2	90
+3	30
+NULL	150
+SELECT DISTINCT a, SUM(b) FROM t1 GROUP BY a WITH ROLLUP;
+a	SUM(b)
+1	30
+2	90
+3	30
+NULL	150
+SELECT a, b, COUNT(*) FROM t1 GROUP BY a,b WITH ROLLUP;
+a	b	COUNT(*)
+1	10	1
+1	20	1
+1	NULL	2
+2	10	2
+2	30	1
+2	40	1
+2	NULL	4
+3	30	1
+3	NULL	1
+NULL	NULL	7
+SELECT DISTINCT a, b, COUNT(*) FROM t1 GROUP BY a,b WITH ROLLUP;
+a	b	COUNT(*)
+1	10	1
+1	20	1
+1	NULL	2
+2	10	2
+2	30	1
+2	40	1
+2	NULL	4
+3	30	1
+3	NULL	1
+NULL	NULL	7
+SELECT 'x', a, SUM(b) FROM t1 GROUP BY 1,2 WITH ROLLUP;
+x	a	SUM(b)
+x	1	30
+x	2	90
+x	3	30
+x	NULL	150
+NULL	NULL	150
+SELECT DISTINCT 'x', a, SUM(b) FROM t1 GROUP BY 1,2 WITH ROLLUP;
+x	a	SUM(b)
+x	1	30
+x	2	90
+x	3	30
+x	NULL	150
+NULL	NULL	150
+SELECT DISTINCT 'x', a, SUM(b) FROM t1 GROUP BY 1,2 WITH ROLLUP;
+x	a	SUM(b)
+x	1	30
+x	2	90
+x	3	30
+x	NULL	150
+NULL	NULL	150
+DROP TABLE t1;
diff --git a/mysql-test/t/olap.test b/mysql-test/t/olap.test
index 683e1402678..99db3874883 100644
--- a/mysql-test/t/olap.test
+++ b/mysql-test/t/olap.test
@@ -281,4 +281,23 @@ select left(a,10), a, sum(b) from t1 group by 1,2 with rollup;
 select left(a,10) x, a, sum(b) from t1 group by x,a with rollup;
 drop table t1;
 
+#
+# Bug #20825: ROLLUP by const item in a query with DISTINCT
+#
+
+CREATE TABLE t1 (a int, b int);
+INSERT INTO t1 
+  VALUES (2,10),(3,30),(2,40),(1,10),(2,30),(1,20),(2,10);
+
+SELECT a, SUM(b) FROM t1 GROUP BY a WITH ROLLUP;
+SELECT DISTINCT a, SUM(b) FROM t1 GROUP BY a WITH ROLLUP;
+SELECT a, b, COUNT(*) FROM t1 GROUP BY a,b WITH ROLLUP;
+SELECT DISTINCT a, b, COUNT(*) FROM t1 GROUP BY a,b WITH ROLLUP;
+
+SELECT 'x', a, SUM(b) FROM t1 GROUP BY 1,2 WITH ROLLUP;
+SELECT DISTINCT 'x', a, SUM(b) FROM t1 GROUP BY 1,2 WITH ROLLUP;
+SELECT DISTINCT 'x', a, SUM(b) FROM t1 GROUP BY 1,2 WITH ROLLUP;
+
+DROP TABLE t1;
+
 # End of 4.1 tests
diff --git a/sql/item_func.h b/sql/item_func.h
index 467b88eda76..ebe3a589aa1 100644
--- a/sql/item_func.h
+++ b/sql/item_func.h
@@ -590,6 +590,31 @@ public:
 };
 
 
+/* 
+  Objects of this class are used for ROLLUP queries to wrap up 
+  each constant item referred to in GROUP BY list. 
+*/
+
+class Item_func_rollup_const :public Item_func
+{
+public:
+  Item_func_rollup_const(Item *a) :Item_func(a)
+    { name= a->name; }
+  double val() { return args[0]->val(); }
+  longlong val_int() { return args[0]->val_int(); }
+  String *val_str(String *str) { return args[0]->val_str(str); }
+  const char *func_name() const { return "rollup_const"; }
+  bool const_item() const { return 0; }
+  Item_result result_type() const { return args[0]->result_type(); }
+  void fix_length_and_dec()
+  {
+    collation= args[0]->collation;
+    max_length= args[0]->max_length;
+    decimals=args[0]->decimals; 
+  }
+};
+
+
 class Item_func_length :public Item_int_func
 {
   String value;
diff --git a/sql/sql_select.cc b/sql/sql_select.cc
index af3ad782ee3..36a15841065 100644
--- a/sql/sql_select.cc
+++ b/sql/sql_select.cc
@@ -9754,7 +9754,7 @@ bool JOIN::rollup_init()
     for (j=0 ; j < fields_list.elements ; j++)
       rollup.fields[i].push_back(rollup.null_items[i]);
   }
-  List_iterator_fast<Item> it(all_fields);
+  List_iterator<Item> it(all_fields);
   Item *item;
   while ((item= it++))
   {
@@ -9767,6 +9767,32 @@ bool JOIN::rollup_init()
       {
         item->maybe_null= 1;
         found_in_group= 1;
+        if (item->const_item())
+        {
+          /*
+            For ROLLUP queries each constant item referenced in GROUP BY list
+            is wrapped up into an Item_func object yielding the same value
+            as the constant item. The objects of the wrapper class are never
+            considered as constant items and besides they inherit all
+            properties of the Item_result_field class.
+            This wrapping allows us to ensure writing constant items
+            into temporary tables whenever the result of the ROLLUP
+            operation has to be written into a temporary table, e.g. when
+            ROLLUP is used together with DISTINCT in the SELECT list.
+            Usually when creating temporary tables for a intermidiate
+            result we do not include fields for constant expressions.
+	  */           
+          Item* new_item= new Item_func_rollup_const(item);
+          if (!new_item)
+            return 1;
+          new_item->fix_fields(thd,0, (Item **) 0);
+          thd->change_item_tree(it.ref(), new_item);
+          for (ORDER *tmp= group_tmp; tmp; tmp= tmp->next)
+          { 
+            if (*tmp->item == item)
+              thd->change_item_tree(tmp->item, new_item);
+          }
+        }
       }
     }
     if (item->type() == Item::FUNC_ITEM && !found_in_group)