diff --git a/mysql-test/main/func_gconcat.result b/mysql-test/main/func_gconcat.result
index fea25124941..7bc6441661b 100644
--- a/mysql-test/main/func_gconcat.result
+++ b/mysql-test/main/func_gconcat.result
@@ -1443,3 +1443,78 @@ drop table t1;
 #
 # End of 10.3 tests
 #
+#
+# MDEV-31276: Execution of PS from grouping query with join
+#             and GROUP_CONCAT set function
+#
+create table t1 (a int, b varchar(20)) engine=myisam;
+create table t2 (a int, c varchar(20)) engine=myisam;
+insert into t1 values (1,"aaaaaaaaaa"),(2,"bbbbbbbbbb");
+insert into t2 values (1,"cccccccccc"),(2,"dddddddddd");
+insert into t2 values (1,"eeeeeee"),(2,"fffffff");
+set group_concat_max_len=5;
+select count(*), group_concat(t1.b,t2.c)
+from t1 join t2 on t1.a=t2.a group by t1.a;
+count(*)	group_concat(t1.b,t2.c)
+2	aaaaa
+2	bbbbb
+Warnings:
+Warning	1260	Row 1 was cut by GROUP_CONCAT()
+Warning	1260	Row 2 was cut by GROUP_CONCAT()
+explain select count(*), group_concat(t1.b,t2.c)
+from t1 join t2 on t1.a=t2.a group by t1.a;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	2	Using temporary; Using filesort
+1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	4	Using where; Using join buffer (flat, BNL join)
+prepare stmt from "select count(*), group_concat(t1.b,t2.c)
+from t1 join t2 on t1.a=t2.a group by t1.a";
+execute stmt;
+count(*)	group_concat(t1.b,t2.c)
+2	aaaaa
+2	bbbbb
+Warnings:
+Warning	1260	Row 1 was cut by GROUP_CONCAT()
+Warning	1260	Row 2 was cut by GROUP_CONCAT()
+execute stmt;
+count(*)	group_concat(t1.b,t2.c)
+2	aaaaa
+2	bbbbb
+Warnings:
+Warning	1260	Row 1 was cut by GROUP_CONCAT()
+Warning	1260	Row 2 was cut by GROUP_CONCAT()
+deallocate prepare stmt;
+set join_cache_level=0;
+select count(*), group_concat(t1.b,t2.c)
+from t1 join t2 on t1.a=t2.a group by t1.a;
+count(*)	group_concat(t1.b,t2.c)
+2	aaaaa
+2	bbbbb
+Warnings:
+Warning	1260	Row 1 was cut by GROUP_CONCAT()
+Warning	1260	Row 2 was cut by GROUP_CONCAT()
+explain select count(*), group_concat(t1.b,t2.c)
+from t1 join t2 on t1.a=t2.a group by t1.a;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	2	Using filesort
+1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	4	Using where
+prepare stmt from "select count(*), group_concat(t1.b,t2.c)
+from t1 join t2 on t1.a=t2.a group by t1.a";
+execute stmt;
+count(*)	group_concat(t1.b,t2.c)
+2	aaaaa
+2	bbbbb
+Warnings:
+Warning	1260	Row 1 was cut by GROUP_CONCAT()
+Warning	1260	Row 2 was cut by GROUP_CONCAT()
+execute stmt;
+count(*)	group_concat(t1.b,t2.c)
+2	aaaaa
+2	bbbbb
+Warnings:
+Warning	1260	Row 1 was cut by GROUP_CONCAT()
+Warning	1260	Row 2 was cut by GROUP_CONCAT()
+deallocate prepare stmt;
+set join_cache_level=default;
+set group_concat_max_len=default;
+drop table t1,t2;
+# End of 10.5 tests
diff --git a/mysql-test/main/func_gconcat.test b/mysql-test/main/func_gconcat.test
index cc5236a18be..2e09bddbb8b 100644
--- a/mysql-test/main/func_gconcat.test
+++ b/mysql-test/main/func_gconcat.test
@@ -1066,3 +1066,43 @@ drop table t1;
 --echo #
 --echo # End of 10.3 tests
 --echo #
+
+--echo #
+--echo # MDEV-31276: Execution of PS from grouping query with join
+--echo #             and GROUP_CONCAT set function
+--echo #
+
+create table t1 (a int, b varchar(20)) engine=myisam;
+create table t2 (a int, c varchar(20)) engine=myisam;
+insert into t1 values (1,"aaaaaaaaaa"),(2,"bbbbbbbbbb");
+insert into t2 values (1,"cccccccccc"),(2,"dddddddddd");
+insert into t2 values (1,"eeeeeee"),(2,"fffffff");
+
+let $q=
+select count(*), group_concat(t1.b,t2.c)
+  from t1 join t2 on t1.a=t2.a group by t1.a;
+
+set group_concat_max_len=5;
+
+eval $q;
+eval explain $q;
+eval prepare stmt from "$q";
+execute stmt;
+execute stmt;
+deallocate prepare stmt;
+
+set join_cache_level=0;
+
+eval $q;
+eval explain $q;
+eval prepare stmt from "$q";
+execute stmt;
+execute stmt;
+deallocate prepare stmt;
+
+set join_cache_level=default;
+set group_concat_max_len=default;
+
+drop table t1,t2;
+
+--echo # End of 10.5 tests
diff --git a/mysql-test/main/join_outer.test b/mysql-test/main/join_outer.test
index da3c82109d8..83bb7fdeef3 100644
--- a/mysql-test/main/join_outer.test
+++ b/mysql-test/main/join_outer.test
@@ -685,15 +685,9 @@ create table t1 (a int, b varchar(20));
 create table t2 (a int, c varchar(20));
 insert into t1 values (1,"aaaaaaaaaa"),(2,"bbbbbbbbbb");
 insert into t2 values (1,"cccccccccc"),(2,"dddddddddd");
-#Enable after fix MDEV-31276
---disable_ps2_protocol
 select group_concat(t1.b,t2.c) from t1 left join t2 using(a) group by t1.a;
---enable_ps2_protocol
 select group_concat(t1.b,t2.c) from t1 inner join t2 using(a) group by t1.a;
-#Enable after fix MDEV-31276
---disable_ps2_protocol
 select group_concat(t1.b,t2.c) from t1 left join t2 using(a) group by a;
---enable_ps2_protocol
 select group_concat(t1.b,t2.c) from t1 inner join t2 using(a) group by a;
 drop table t1, t2;
 set group_concat_max_len=default;
diff --git a/mysql-test/main/subselect_sj_mat.test b/mysql-test/main/subselect_sj_mat.test
index 000581d5758..6b343900dca 100644
--- a/mysql-test/main/subselect_sj_mat.test
+++ b/mysql-test/main/subselect_sj_mat.test
@@ -523,8 +523,6 @@ where a1 in (select substring(b1,1,512) from t2_512 where b1 > '0');
 # group_concat with a blob argument - depends on
 # the variable group_concat_max_len, and
 # convert_blob_length == max_len*collation->mbmaxlen > CONVERT_IF_BIGGER_TO_BLOB
-#Check after fix MDEV-31276
---disable_ps2_protocol
 explain extended select left(a1,7), left(a2,7)
 from t1_512
 where a1 in (select group_concat(b1) from t2_512 group by b2);
@@ -542,7 +540,6 @@ where a1 in (select group_concat(b1) from t2_512 group by b2);
 select left(a1,7), left(a2,7)
 from t1_512
 where a1 in (select group_concat(b1) from t2_512 group by b2);
---enable_ps2_protocol
 
 drop table t1_512, t2_512, t3_512;
 
@@ -608,8 +605,6 @@ where a1 in (select substring(b1,1,1024) from t2_1024 where b1 > '0');
 # group_concat with a blob argument - depends on
 # the variable group_concat_max_len, and
 # convert_blob_length == max_len*collation->mbmaxlen > CONVERT_IF_BIGGER_TO_BLOB
-#Check after fix MDEV-31276
---disable_ps2_protocol
 explain extended select left(a1,7), left(a2,7)
 from t1_1024
 where a1 in (select group_concat(b1) from t2_1024 group by b2);
@@ -627,7 +622,6 @@ where a1 in (select group_concat(b1) from t2_1024 group by b2);
 select left(a1,7), left(a2,7)
 from t1_1024
 where a1 in (select group_concat(b1) from t2_1024 group by b2);
---enable_ps2_protocol
 
 drop table t1_1024, t2_1024, t3_1024;
 
@@ -693,8 +687,6 @@ where a1 in (select substring(b1,1,1025) from t2_1025 where b1 > '0');
 # group_concat with a blob argument - depends on
 # the variable group_concat_max_len, and
 # convert_blob_length == max_len*collation->mbmaxlen > CONVERT_IF_BIGGER_TO_BLOB
-#Check after fix MDEV-31276
---disable_ps2_protocol
 explain extended select left(a1,7), left(a2,7)
 from t1_1025
 where a1 in (select group_concat(b1) from t2_1025 group by b2);
@@ -712,7 +704,6 @@ where a1 in (select group_concat(b1) from t2_1025 group by b2);
 select left(a1,7), left(a2,7)
 from t1_1025
 where a1 in (select group_concat(b1) from t2_1025 group by b2);
---enable_ps2_protocol
 
 drop table t1_1025, t2_1025, t3_1025;
 
diff --git a/sql/item_sum.cc b/sql/item_sum.cc
index 99e1d622bf8..7f39efe6c9a 100644
--- a/sql/item_sum.cc
+++ b/sql/item_sum.cc
@@ -4056,6 +4056,7 @@ void Item_func_group_concat::cleanup()
         unique_filter= NULL;
       }
     }
+    row_count= 0;
     DBUG_ASSERT(tree == 0);
   }
   /*