diff --git a/mysql-test/suite/sys_vars/r/character_set_client_basic.result b/mysql-test/suite/sys_vars/r/character_set_client_basic.result
index d62d88027c7..14c8bcfd058 100644
--- a/mysql-test/suite/sys_vars/r/character_set_client_basic.result
+++ b/mysql-test/suite/sys_vars/r/character_set_client_basic.result
@@ -500,5 +500,16 @@ res
 #
 SET GLOBAL character_set_client=2;
 ERROR 42000: Unknown character set: '2'
+#
+# MDEV-31018 Replica of 10.3, 10.4, <10.5.19 and <10.6.12 to 10.11 will not work when using non-default charset
+#
+SET @@pseudo_slave_mode=1;
+SET character_set_client=2/*latin2_czech_cs*/;
+SHOW VARIABLES LIKE 'character_set_client';
+Variable_name	Value
+character_set_client	latin2
+SET @@pseudo_slave_mode=0;
+Warnings:
+Warning	1231	Slave applier execution mode not active, statement ineffective.
 SET @@global.character_set_client = @global_start_value;
 SET @@session.character_set_client = @session_start_value;
diff --git a/mysql-test/suite/sys_vars/r/character_set_connection_basic.result b/mysql-test/suite/sys_vars/r/character_set_connection_basic.result
index e356d62ed2b..bbb4f4e5f75 100644
--- a/mysql-test/suite/sys_vars/r/character_set_connection_basic.result
+++ b/mysql-test/suite/sys_vars/r/character_set_connection_basic.result
@@ -494,5 +494,21 @@ SELECT @@session.character_set_connection =
 WHERE VARIABLE_NAME='character_set_connection') AS res;
 res
 1
+#
+# MDEV-31018 Replica of 10.3, 10.4, <10.5.19 and <10.6.12 to 10.11 will not work when using non-default charset
+#
+SET character_set_connection=2/*latin2_czech_cs*/;
+ERROR 42000: Unknown character set: '2'
+SET @@pseudo_slave_mode=1;
+SET character_set_connection=2/*latin2_czech_cs*/;
+SHOW VARIABLES LIKE 'character_set_connection';
+Variable_name	Value
+character_set_connection	latin2
+SHOW VARIABLES LIKE 'collation_connection';
+Variable_name	Value
+collation_connection	latin2_general_ci
+SET @@pseudo_slave_mode=0;
+Warnings:
+Warning	1231	Slave applier execution mode not active, statement ineffective.
 SET @@global.character_set_connection = @global_start_value;
 SET @@global.character_set_client = @save_character_set_client;
diff --git a/mysql-test/suite/sys_vars/r/character_set_results_basic.result b/mysql-test/suite/sys_vars/r/character_set_results_basic.result
index d1c6a52ba17..1346c8b42ca 100644
Binary files a/mysql-test/suite/sys_vars/r/character_set_results_basic.result and b/mysql-test/suite/sys_vars/r/character_set_results_basic.result differ
diff --git a/mysql-test/suite/sys_vars/r/character_set_server_basic.result b/mysql-test/suite/sys_vars/r/character_set_server_basic.result
index e0a13c729fe..7445be6aef1 100644
--- a/mysql-test/suite/sys_vars/r/character_set_server_basic.result
+++ b/mysql-test/suite/sys_vars/r/character_set_server_basic.result
@@ -486,5 +486,21 @@ SELECT @@session.character_set_server =
 WHERE VARIABLE_NAME='character_set_server') AS res;
 res
 1
+#
+# MDEV-31018 Replica of 10.3, 10.4, <10.5.19 and <10.6.12 to 10.11 will not work when using non-default charset
+#
+SET character_set_server=2/*latin2_czech_cs*/;
+ERROR 42000: Unknown character set: '2'
+SET @@pseudo_slave_mode=1;
+SET character_set_server=2/*latin2_czech_cs*/;
+SHOW VARIABLES LIKE 'character_set_server';
+Variable_name	Value
+character_set_server	latin2
+SHOW VARIABLES LIKE 'collation_server';
+Variable_name	Value
+collation_server	latin2_general_ci
+SET @@pseudo_slave_mode=0;
+Warnings:
+Warning	1231	Slave applier execution mode not active, statement ineffective.
 SET @@global.character_set_server = @global_start_value;
 SET @@session.character_set_server = @session_start_value;
diff --git a/mysql-test/suite/sys_vars/t/character_set_client_basic.test b/mysql-test/suite/sys_vars/t/character_set_client_basic.test
index 09f758a0316..44c0d240a9d 100644
--- a/mysql-test/suite/sys_vars/t/character_set_client_basic.test
+++ b/mysql-test/suite/sys_vars/t/character_set_client_basic.test
@@ -350,6 +350,15 @@ SELECT @@session.character_set_client =
 --error ER_UNKNOWN_CHARACTER_SET
 SET GLOBAL character_set_client=2;
 
+--echo #
+--echo # MDEV-31018 Replica of 10.3, 10.4, <10.5.19 and <10.6.12 to 10.11 will not work when using non-default charset
+--echo #
+
+SET @@pseudo_slave_mode=1;
+SET character_set_client=2/*latin2_czech_cs*/;
+SHOW VARIABLES LIKE 'character_set_client';
+SET @@pseudo_slave_mode=0;
+
 ####################################
 #     Restore initial value        #
 ####################################
diff --git a/mysql-test/suite/sys_vars/t/character_set_connection_basic.test b/mysql-test/suite/sys_vars/t/character_set_connection_basic.test
index 3d9094fca04..46bdfcb52e2 100644
--- a/mysql-test/suite/sys_vars/t/character_set_connection_basic.test
+++ b/mysql-test/suite/sys_vars/t/character_set_connection_basic.test
@@ -275,6 +275,19 @@ SELECT @@session.character_set_connection =
  (SELECT VARIABLE_VALUE FROM INFORMATION_SCHEMA.SESSION_VARIABLES
   WHERE VARIABLE_NAME='character_set_connection') AS res;
 
+--echo #
+--echo # MDEV-31018 Replica of 10.3, 10.4, <10.5.19 and <10.6.12 to 10.11 will not work when using non-default charset
+--echo #
+
+--error ER_UNKNOWN_CHARACTER_SET
+SET character_set_connection=2/*latin2_czech_cs*/;
+SET @@pseudo_slave_mode=1;
+SET character_set_connection=2/*latin2_czech_cs*/;
+SHOW VARIABLES LIKE 'character_set_connection';
+SHOW VARIABLES LIKE 'collation_connection';
+SET @@pseudo_slave_mode=0;
+
+
 ####################################
 #     Restore initial value        #
 ####################################
diff --git a/mysql-test/suite/sys_vars/t/character_set_results_basic.test b/mysql-test/suite/sys_vars/t/character_set_results_basic.test
index 617332b9780..41090be6657 100644
--- a/mysql-test/suite/sys_vars/t/character_set_results_basic.test
+++ b/mysql-test/suite/sys_vars/t/character_set_results_basic.test
@@ -272,6 +272,18 @@ SELECT @@session.character_set_results =
  (SELECT VARIABLE_VALUE FROM INFORMATION_SCHEMA.SESSION_VARIABLES
   WHERE VARIABLE_NAME='character_set_results') AS res;
 
+--echo #
+--echo # MDEV-31018 Replica of 10.3, 10.4, <10.5.19 and <10.6.12 to 10.11 will not work when using non-default charset
+--echo #
+
+--error ER_UNKNOWN_CHARACTER_SET
+SET character_set_results=2/*latin2_czech_cs*/;
+SET @@pseudo_slave_mode=1;
+SET character_set_results=2;
+SHOW VARIABLES LIKE 'character_set_results';
+SET @@pseudo_slave_mode=0;
+
+
 ####################################
 #     Restore initial value        #
 ####################################
diff --git a/mysql-test/suite/sys_vars/t/character_set_server_basic.test b/mysql-test/suite/sys_vars/t/character_set_server_basic.test
index b2f4788fdae..929dbfaf143 100644
--- a/mysql-test/suite/sys_vars/t/character_set_server_basic.test
+++ b/mysql-test/suite/sys_vars/t/character_set_server_basic.test
@@ -266,6 +266,18 @@ SELECT @@session.character_set_server =
  (SELECT VARIABLE_VALUE FROM INFORMATION_SCHEMA.SESSION_VARIABLES
   WHERE VARIABLE_NAME='character_set_server') AS res;
 
+--echo #
+--echo # MDEV-31018 Replica of 10.3, 10.4, <10.5.19 and <10.6.12 to 10.11 will not work when using non-default charset
+--echo #
+
+--error ER_UNKNOWN_CHARACTER_SET
+SET character_set_server=2/*latin2_czech_cs*/;
+SET @@pseudo_slave_mode=1;
+SET character_set_server=2/*latin2_czech_cs*/;
+SHOW VARIABLES LIKE 'character_set_server';
+SHOW VARIABLES LIKE 'collation_server';
+SET @@pseudo_slave_mode=0;
+
 ####################################
 #     Restore initial value        #
 ####################################
diff --git a/sql/sys_vars.cc b/sql/sys_vars.cc
index 10f9de106f8..45b5fe20ff6 100644
--- a/sql/sys_vars.cc
+++ b/sql/sys_vars.cc
@@ -791,12 +791,26 @@ static bool check_charset(sys_var *self, THD *thd, set_var *var)
   {
     int csno= (int)var->value->val_int();
     CHARSET_INFO *cs;
-    if (!(var->save_result.ptr= cs= get_charset(csno, MYF(0))) ||
-        !(cs->state & MY_CS_PRIMARY))
+    if ((var->save_result.ptr= cs= get_charset(csno, MYF(0))))
     {
-      my_error(ER_UNKNOWN_CHARACTER_SET, MYF(0), llstr(csno, buff));
-      return true;
+      /*
+        Backward compatibility: pre MDEV-30824 servers
+        can write non-default collation IDs to binary log:
+          SET character_set_client=83; -- utf8mb3_bin
+        Convert a non-default collation to the compiled default collation,
+        e.g. utf8mb3_bin to utf8mb3_general_ci, but only if
+        - THD is a slave thread or
+        - is processing a mysqlbinlog output.
+      */
+      if ((cs->state & MY_CS_PRIMARY) ||
+          ((thd->variables.pseudo_slave_mode || thd->slave_thread) &&
+           (var->save_result.ptr=
+             Lex_exact_charset_opt_extended_collate(cs, true).
+               find_default_collation())))
+        return false;
     }
+    my_error(ER_UNKNOWN_CHARACTER_SET, MYF(0), llstr(csno, buff));
+    return true;
   }
   return false;
 }