diff --git a/mysql-test/main/sp.result b/mysql-test/main/sp.result
index 567597383bb..2f733107e8a 100644
--- a/mysql-test/main/sp.result
+++ b/mysql-test/main/sp.result
@@ -8960,5 +8960,20 @@ DROP FUNCTION f1;
 DROP FUNCTION f2;
 DROP FUNCTION f3;
 DROP VIEW v1;
+#
+# MDEV-33270: Call of SP invoking another SP with a parameter
+#             requiring type conversion
+#
+SET NAMES latin1;
+CREATE PROCEDURE p1 (a text) BEGIN SELECT a; END |
+CREATE PROCEDURE p2 () CALL p1(concat('x',_utf8'x')) |
+CALL p2();
+a
+xx
+CALL p2();
+a
+xx
+DROP PROCEDURE p1;
+DROP PROCEDURE p2;
 # End of 10.4 tests
 #
diff --git a/mysql-test/main/sp.test b/mysql-test/main/sp.test
index c11ea23080b..50d9a611db9 100644
--- a/mysql-test/main/sp.test
+++ b/mysql-test/main/sp.test
@@ -10567,5 +10567,25 @@ DROP FUNCTION f2;
 DROP FUNCTION f3;
 DROP VIEW v1;
 
+--echo #
+--echo # MDEV-33270: Call of SP invoking another SP with a parameter
+--echo #             requiring type conversion
+--echo #
+
+SET NAMES latin1;
+
+--delimiter |
+
+CREATE PROCEDURE p1 (a text) BEGIN SELECT a; END |
+CREATE PROCEDURE p2 () CALL p1(concat('x',_utf8'x')) |
+
+--delimiter ;
+
+CALL p2();
+CALL p2();
+
+DROP PROCEDURE p1;
+DROP PROCEDURE p2;
+
 --echo # End of 10.4 tests
 --echo #
diff --git a/sql/item.cc b/sql/item.cc
index 6d30d63bc11..04b689f51af 100644
--- a/sql/item.cc
+++ b/sql/item.cc
@@ -2586,7 +2586,10 @@ bool Type_std_attributes::agg_item_set_converter(const DTCollation &coll,
       return TRUE;
 
     if (!thd->stmt_arena->is_conventional() &&
-        thd->lex->current_select->first_cond_optimization)
+	((!thd->lex->current_select &&
+	  (thd->stmt_arena->is_stmt_prepare_or_first_sp_execute() ||
+           thd->stmt_arena->is_stmt_prepare_or_first_stmt_execute())) ||
+         thd->lex->current_select->first_cond_optimization))
     {
       Query_arena *arena, backup;
       arena= thd->activate_stmt_arena_if_needed(&backup);