diff --git a/mysql-test/main/cte_recursive.result b/mysql-test/main/cte_recursive.result
index 0b7b216f1fe..63fcb63c7ee 100644
--- a/mysql-test/main/cte_recursive.result
+++ b/mysql-test/main/cte_recursive.result
@@ -5800,4 +5800,52 @@ a	a
 9	9
 10	10
 drop table t1;
+#
+# MDEV-20010 Equal on two RANK window functions create wrong result
+#
+create table t1 (a int, b int) engine= innodb;
+insert into t1 values (4, -2), (3, -1);
+SELECT RANK() OVER (ORDER BY D.C) = RANK() OVER (ORDER BY B.a) FROM
+(SELECT 5 AS C FROM t1) as D, (SELECT t1.b AS A FROM t1) AS B;
+RANK() OVER (ORDER BY D.C) = RANK() OVER (ORDER BY B.a)
+1
+1
+0
+0
+select b, rank() over (order by c) , rank() over (order by dt1.b)
+from
+(select 5 as c from t1) as dt,
+(select b from t1) as dt1;
+b	rank() over (order by c)	rank() over (order by dt1.b)
+-2	1	1
+-2	1	1
+-1	1	3
+-1	1	3
+select b, rank() over (order by c) , rank() over (order by dt1.b),
+rank() over (order by c) = rank() over (order by dt1.b)
+from
+(select 5 as c from t1) as dt,
+(select b from t1) as dt1;
+b	rank() over (order by c)	rank() over (order by dt1.b)	rank() over (order by c) = rank() over (order by dt1.b)
+-2	1	1	1
+-2	1	1	1
+-1	1	3	0
+-1	1	3	0
+alter table t1 engine=myisam;
+select b, rank() over (order by c) , rank() over (order by dt1.b)
+from
+(select 5 as c from t1) as dt,
+(select b from t1) as dt1;
+b	rank() over (order by c)	rank() over (order by dt1.b)
+-2	1	1
+-2	1	1
+-1	1	3
+-1	1	3
+create view v1 as select b,5 as c from t1;
+select b, rank() over (order by c) from v1 order by b;
+b	rank() over (order by c)
+-2	1
+-1	1
+drop view v1;
+drop table t1;
 # End of 10.4 tests
diff --git a/mysql-test/main/cte_recursive.test b/mysql-test/main/cte_recursive.test
index 4d21a494bdc..6053025499a 100644
--- a/mysql-test/main/cte_recursive.test
+++ b/mysql-test/main/cte_recursive.test
@@ -1,4 +1,5 @@
 --source include/default_optimizer_switch.inc
+--source include/have_innodb.inc
 
 create table t1 (a int, b varchar(32));
 insert into t1 values
@@ -4013,4 +4014,37 @@ with cte_e as (
 
 drop table t1;
 
+--echo #
+--echo # MDEV-20010 Equal on two RANK window functions create wrong result
+--echo #
+
+create table t1 (a int, b int) engine= innodb;
+insert into t1 values (4, -2), (3, -1);
+
+SELECT RANK() OVER (ORDER BY D.C) = RANK() OVER (ORDER BY B.a) FROM
+(SELECT 5 AS C FROM t1) as D, (SELECT t1.b AS A FROM t1) AS B;
+
+select b, rank() over (order by c) , rank() over (order by dt1.b)
+from
+(select 5 as c from t1) as dt,
+(select b from t1) as dt1;
+
+select b, rank() over (order by c) , rank() over (order by dt1.b),
+rank() over (order by c) = rank() over (order by dt1.b)
+from
+(select 5 as c from t1) as dt,
+(select b from t1) as dt1;
+
+alter table t1 engine=myisam;
+select b, rank() over (order by c) , rank() over (order by dt1.b)
+from
+(select 5 as c from t1) as dt,
+(select b from t1) as dt1;
+
+create view v1 as select b,5 as c from t1;
+select b, rank() over (order by c) from v1 order by b;
+
+drop view v1;
+drop table t1;
+
 --echo # End of 10.4 tests
diff --git a/sql/sql_window.cc b/sql/sql_window.cc
index ff7554b0cd7..df43efe18a4 100644
--- a/sql/sql_window.cc
+++ b/sql/sql_window.cc
@@ -3076,7 +3076,7 @@ bool Window_funcs_sort::setup(THD *thd, SQL_SELECT *sel,
     spec= win_func->window_spec;
     int win_func_order_elements= spec->partition_list->elements +
                                   spec->order_list->elements;
-    if (win_func_order_elements > longest_order_elements)
+    if (win_func_order_elements >= longest_order_elements)
     {
       win_func_with_longest_order= win_func;
       longest_order_elements= win_func_order_elements;