diff --git a/mysql-test/r/win_avg.result b/mysql-test/r/win_avg.result
new file mode 100644
index 00000000000..7e539d933d8
--- /dev/null
+++ b/mysql-test/r/win_avg.result
@@ -0,0 +1,95 @@
+create table t1 (
+pk int primary key,
+a int,
+b int,
+c real
+);
+insert into t1 values
+(101 , 0, 10, 1.1),
+(102 , 0, 10, 2.1),
+(103 , 1, 10, 3.1),
+(104 , 1, 10, 4.1),
+(108 , 2, 10, 5.1),
+(105 , 2, 20, 6.1),
+(106 , 2, 20, 7.1),
+(107 , 2, 20, 8.15),
+(109 , 4, 20, 9.15),
+(110 , 4, 20, 10.15),
+(111 , 5, NULL, 11.15),
+(112 , 5, 1, 12.25),
+(113 , 5, NULL, 13.35),
+(114 , 5, NULL, 14.50),
+(115 , 5, NULL, 15.65),
+(116 , 6, 1, NULL),
+(117 , 6, 1, 10),
+(118 , 6, 1, 1.1),
+(119 , 6, 1, NULL),
+(120 , 6, 1, NULL),
+(121 , 6, 1, NULL),
+(122 , 6, 1, 2.2),
+(123 , 6, 1, 20.1),
+(124 , 6, 1, -10.4),
+(125 , 6, 1, NULL),
+(126 , 6, 1, NULL),
+(127 , 6, 1, NULL);
+select pk, a, b, avg(b) over (partition by a order by pk ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING)
+from t1;
+pk	a	b	avg(b) over (partition by a order by pk ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING)
+101	0	10	10.0000
+102	0	10	10.0000
+103	1	10	10.0000
+104	1	10	10.0000
+105	2	20	20.0000
+106	2	20	20.0000
+107	2	20	16.6667
+108	2	10	15.0000
+109	4	20	20.0000
+110	4	20	20.0000
+111	5	NULL	1.0000
+112	5	1	1.0000
+113	5	NULL	1.0000
+114	5	NULL	NULL
+115	5	NULL	NULL
+116	6	1	1.0000
+117	6	1	1.0000
+118	6	1	1.0000
+119	6	1	1.0000
+120	6	1	1.0000
+121	6	1	1.0000
+122	6	1	1.0000
+123	6	1	1.0000
+124	6	1	1.0000
+125	6	1	1.0000
+126	6	1	1.0000
+127	6	1	1.0000
+select pk, a, c, avg(c) over (partition by a order by pk ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING)
+from t1;
+pk	a	c	avg(c) over (partition by a order by pk ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING)
+101	0	1.1	1.6
+102	0	2.1	1.6
+103	1	3.1	3.5999999999999996
+104	1	4.1	3.5999999999999996
+105	2	6.1	6.6
+106	2	7.1	7.116666666666667
+107	2	8.15	6.783333333333334
+108	2	5.1	6.625000000000001
+109	4	9.15	9.65
+110	4	10.15	9.65
+111	5	11.15	11.7
+112	5	12.25	12.25
+113	5	13.35	13.366666666666667
+114	5	14.5	14.5
+115	5	15.65	15.075
+116	6	NULL	10
+117	6	10	5.55
+118	6	1.1	5.55
+119	6	NULL	1.0999999999999996
+120	6	NULL	NULL
+121	6	NULL	2.1999999999999997
+122	6	2.2	11.15
+123	6	20.1	3.966666666666667
+124	6	-10.4	4.85
+125	6	NULL	-10.400000000000002
+126	6	NULL	NULL
+127	6	NULL	NULL
+drop table t1;
diff --git a/mysql-test/t/win_avg.test b/mysql-test/t/win_avg.test
new file mode 100644
index 00000000000..23a3652d943
--- /dev/null
+++ b/mysql-test/t/win_avg.test
@@ -0,0 +1,47 @@
+create table t1 (
+  pk int primary key,
+  a int,
+  b int,
+  c real
+);
+
+
+insert into t1 values
+(101 , 0, 10, 1.1),
+(102 , 0, 10, 2.1),
+(103 , 1, 10, 3.1),
+(104 , 1, 10, 4.1),
+(108 , 2, 10, 5.1),
+(105 , 2, 20, 6.1),
+(106 , 2, 20, 7.1),
+(107 , 2, 20, 8.15),
+(109 , 4, 20, 9.15),
+(110 , 4, 20, 10.15),
+(111 , 5, NULL, 11.15),
+(112 , 5, 1, 12.25),
+(113 , 5, NULL, 13.35),
+(114 , 5, NULL, 14.50),
+(115 , 5, NULL, 15.65),
+(116 , 6, 1, NULL),
+(117 , 6, 1, 10),
+(118 , 6, 1, 1.1),
+(119 , 6, 1, NULL),
+(120 , 6, 1, NULL),
+(121 , 6, 1, NULL),
+(122 , 6, 1, 2.2),
+(123 , 6, 1, 20.1),
+(124 , 6, 1, -10.4),
+(125 , 6, 1, NULL),
+(126 , 6, 1, NULL),
+(127 , 6, 1, NULL);
+
+
+--sorted_result
+select pk, a, b, avg(b) over (partition by a order by pk ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING)
+from t1;
+
+--sorted_result
+select pk, a, c, avg(c) over (partition by a order by pk ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING)
+from t1;
+
+drop table t1;
diff --git a/sql/item_sum.cc b/sql/item_sum.cc
index b7490d02233..4b4ed0225d3 100644
--- a/sql/item_sum.cc
+++ b/sql/item_sum.cc
@@ -1681,6 +1681,16 @@ bool Item_sum_avg::add()
   return FALSE;
 }
 
+void Item_sum_avg::remove()
+{
+  Item_sum_sum::remove();
+  if (!aggr->arg_is_null(true))
+  {
+    DBUG_ASSERT(count > 0);
+    count--;
+  }
+}
+
 double Item_sum_avg::val_real()
 {
   DBUG_ASSERT(fixed == 1);
diff --git a/sql/item_sum.h b/sql/item_sum.h
index 6698a1b2169..b8f41030465 100644
--- a/sql/item_sum.h
+++ b/sql/item_sum.h
@@ -837,6 +837,8 @@ class Item_sum_count :public Item_sum_int
 class Item_sum_avg :public Item_sum_sum
 {
 public:
+  // TODO-cvicentiu given that Item_sum_sum now uses a counter of its own, in
+  // order to implement remove(), it is possible to remove this member.
   ulonglong count;
   uint prec_increment;
   uint f_precision, f_scale, dec_bin_size;
@@ -855,6 +857,7 @@ public:
   }
   void clear();
   bool add();
+  void remove();
   double val_real();
   // In SPs we might force the "wrong" type with select into a declare variable
   longlong val_int() { return val_int_from_real(); }
diff --git a/sql/sql_window.cc b/sql/sql_window.cc
index f0d74b15e7c..efdb5aa91a0 100644
--- a/sql/sql_window.cc
+++ b/sql/sql_window.cc
@@ -1585,6 +1585,7 @@ bool JOIN::process_window_functions(List<Item> *curr_fields_list)
           case Item_sum::COUNT_FUNC:
           case Item_sum::SUM_BIT_FUNC:
           case Item_sum::SUM_FUNC:
+          case Item_sum::AVG_FUNC:
           {
             /*
               Frame-aware window function computation. It does one pass, but