diff --git a/mysql-test/r/win_percent_cume.result b/mysql-test/r/win_percent_cume.result
new file mode 100644
index 00000000000..d38c95c9ea7
--- /dev/null
+++ b/mysql-test/r/win_percent_cume.result
@@ -0,0 +1,62 @@
+create table t1 (
+pk int primary key,
+a int,
+b int
+);
+insert into t1 values
+( 1 , 0, 10),
+( 2 , 0, 10),
+( 3 , 1, 10),
+( 4 , 1, 10),
+( 8 , 2, 10),
+( 5 , 2, 20),
+( 6 , 2, 20),
+( 7 , 2, 20),
+( 9 , 4, 20),
+(10 , 4, 20);
+select pk, a, b,
+percent_rank() over (order by a),
+cume_dist() over (order by a)
+from t1;
+pk	a	b	percent_rank() over (order by a)	cume_dist() over (order by a)
+1	0	10	0.0000000000	0.2000000000
+2	0	10	0.0000000000	0.2000000000
+3	1	10	0.2222222222	0.4000000000
+4	1	10	0.2222222222	0.4000000000
+8	2	10	0.4444444444	0.8000000000
+5	2	20	0.4444444444	0.8000000000
+6	2	20	0.4444444444	0.8000000000
+7	2	20	0.4444444444	0.8000000000
+9	4	20	0.8888888889	1.0000000000
+10	4	20	0.8888888889	1.0000000000
+select pk, a, b,
+percent_rank() over (order by pk),
+cume_dist() over (order by pk)
+from t1 order by pk;
+pk	a	b	percent_rank() over (order by pk)	cume_dist() over (order by pk)
+1	0	10	0.0000000000	0.1000000000
+2	0	10	0.1111111111	0.2000000000
+3	1	10	0.2222222222	0.3000000000
+4	1	10	0.3333333333	0.4000000000
+5	2	20	0.4444444444	0.5000000000
+6	2	20	0.5555555556	0.6000000000
+7	2	20	0.6666666667	0.7000000000
+8	2	10	0.7777777778	0.8000000000
+9	4	20	0.8888888889	0.9000000000
+10	4	20	1.0000000000	1.0000000000
+select pk, a, b,
+percent_rank() over (partition by a order by a),
+cume_dist() over (partition by a order by a)
+from t1;
+pk	a	b	percent_rank() over (partition by a order by a)	cume_dist() over (partition by a order by a)
+1	0	10	0.0000000000	1.0000000000
+2	0	10	0.0000000000	1.0000000000
+3	1	10	0.0000000000	1.0000000000
+4	1	10	0.0000000000	1.0000000000
+8	2	10	0.0000000000	1.0000000000
+5	2	20	0.0000000000	1.0000000000
+6	2	20	0.0000000000	1.0000000000
+7	2	20	0.0000000000	1.0000000000
+9	4	20	0.0000000000	1.0000000000
+10	4	20	0.0000000000	1.0000000000
+drop table t1;
diff --git a/mysql-test/t/win_percent_cume.test b/mysql-test/t/win_percent_cume.test
new file mode 100644
index 00000000000..b851185cb32
--- /dev/null
+++ b/mysql-test/t/win_percent_cume.test
@@ -0,0 +1,36 @@
+create table t1 (
+  pk int primary key,
+  a int,
+  b int
+);
+
+
+insert into t1 values
+( 1 , 0, 10),
+( 2 , 0, 10),
+( 3 , 1, 10),
+( 4 , 1, 10),
+( 8 , 2, 10),
+( 5 , 2, 20),
+( 6 , 2, 20),
+( 7 , 2, 20),
+( 9 , 4, 20),
+(10 , 4, 20);
+
+select pk, a, b,
+    percent_rank() over (order by a),
+    cume_dist() over (order by a)
+from t1;
+
+select pk, a, b,
+       percent_rank() over (order by pk),
+       cume_dist() over (order by pk)
+from t1 order by pk;
+
+select pk, a, b,
+        percent_rank() over (partition by a order by a),
+        cume_dist() over (partition by a order by a)
+from t1;
+
+drop table t1;
+
diff --git a/sql/item_windowfunc.h b/sql/item_windowfunc.h
index 1dd483ca9b3..59b739767c8 100644
--- a/sql/item_windowfunc.h
+++ b/sql/item_windowfunc.h
@@ -422,27 +422,62 @@ class Item_sum_percent_rank: public Item_sum_window_with_row_count
     window ordering of the window partition of R
   - NR is defined to be the number of rows in the window partition of R.
 
-  Just like with Item_sum_percent_rank, compuation of this function requires
+  Just like with Item_sum_percent_rank, computation of this function requires
   two passes.
 */
 
-class Item_sum_cume_dist: public Item_sum_percent_rank
+class Item_sum_cume_dist: public Item_sum_window_with_row_count
 {
  public:
-  Item_sum_cume_dist(THD *thd)
-    : Item_sum_percent_rank(thd) {}
+  Item_sum_cume_dist(THD *thd) : Item_sum_window_with_row_count(thd),
+                                 current_row_count_(0) {}
 
-  double val_real() { return 0; }
+  double val_real()
+  {
+    if (get_row_count() == 0)
+    {
+      null_value= true;
+      return 0;
+    }
+    ulonglong partition_row_count= get_row_count();
+    null_value= false;
+    return static_cast<double>(current_row_count_) / partition_row_count;
+  }
+
+  bool add()
+  {
+    current_row_count_++;
+    return false;
+  }
 
   enum Sumfunctype sum_func () const
   {
     return CUME_DIST_FUNC;
   }
 
+  void clear()
+  {
+    current_row_count_= 0;
+    set_row_count(0);
+  }
+
   const char*func_name() const
   {
     return "cume_dist";
   }
+
+  void update_field() {}
+  enum Item_result result_type () const { return REAL_RESULT; }
+  enum_field_types field_type() const { return MYSQL_TYPE_DOUBLE; }
+
+  void fix_length_and_dec()
+  {
+    decimals = 10;  // TODO-cvicentiu find out how many decimals the standard
+                    // requires.
+  }
+
+ private:
+  ulonglong current_row_count_;
 };
 
 
diff --git a/sql/sql_window.cc b/sql/sql_window.cc
index 1bfac7ad3cf..f605ed8718d 100644
--- a/sql/sql_window.cc
+++ b/sql/sql_window.cc
@@ -923,8 +923,8 @@ class Frame_unbounded_following_set_count : public Frame_unbounded_following
       /* Read the first row */
       if (cursor.get_next())
         return;
-      num_rows_in_partition++;
     }
+    num_rows_in_partition++;
 
     /* Remember which partition we are in */
     bound_tracker.check_if_next_group();
@@ -1412,8 +1412,6 @@ bool compute_window_func_with_frames(Item_window_func *item_win,
 }
 
 
-
-
 /* Make a list that is a concation of two lists of ORDER elements */
 
 static ORDER* concat_order_lists(MEM_ROOT *mem_root, ORDER *list1, ORDER *list2)