diff --git a/mysql-test/main/cte_recursive.result b/mysql-test/main/cte_recursive.result
index 6fccd39e59d..19a2e964959 100644
--- a/mysql-test/main/cte_recursive.result
+++ b/mysql-test/main/cte_recursive.result
@@ -3509,3 +3509,22 @@ Beijing
 Bangkok
 Paris
 drop table flights, distances;
+#
+# MDEV-15159: Forced nullability of columns in recursive CTE
+#
+WITH RECURSIVE cte AS (
+SELECT 1 AS a UNION ALL
+SELECT NULL FROM cte WHERE a IS NOT NULL)
+SELECT * FROM cte;
+a
+1
+NULL
+CREATE TABLE t1 (a int NOT NULL);
+INSERT INTO t1 VALUES (0);
+WITH RECURSIVE cte AS
+(SELECT a FROM t1 where a=0 UNION SELECT NULL FROM cte)
+SELECT * FROM cte;
+a
+0
+NULL
+DROP TABLE t1;
diff --git a/mysql-test/main/cte_recursive.test b/mysql-test/main/cte_recursive.test
index 9d7f23a2258..b0b38a28b34 100644
--- a/mysql-test/main/cte_recursive.test
+++ b/mysql-test/main/cte_recursive.test
@@ -2458,3 +2458,21 @@ with recursive destinations (city) as
 select * from destinations;
 
 drop table flights, distances;
+
+--echo #
+--echo # MDEV-15159: Forced nullability of columns in recursive CTE
+--echo #
+
+WITH RECURSIVE cte AS (
+	SELECT 1 AS a UNION ALL
+	SELECT NULL FROM cte WHERE a IS NOT NULL)
+SELECT * FROM cte;
+
+CREATE TABLE t1 (a int NOT NULL);
+INSERT INTO t1 VALUES (0);
+
+WITH RECURSIVE cte AS
+  (SELECT a FROM t1 where a=0 UNION SELECT NULL FROM cte)
+SELECT * FROM cte;
+
+DROP TABLE t1;
diff --git a/sql/sql_union.cc b/sql/sql_union.cc
index 9b9418f0d29..971bb64cf2e 100644
--- a/sql/sql_union.cc
+++ b/sql/sql_union.cc
@@ -788,18 +788,28 @@ bool st_select_lex_unit::join_union_item_types(THD *thd_arg,
      join_union_type_attributes(thd_arg, holders, count))
     DBUG_RETURN(true);
 
+  bool is_recursive= with_element && with_element->is_recursive;
   types.empty();
   List_iterator_fast<Item> it(first_sl->item_list);
   Item *item_tmp;
   for (uint pos= 0; (item_tmp= it++); pos++)
   {
+    /*
+      SQL standard requires forced nullability only for
+      recursive columns. However type aggregation in our
+      implementation so far does not differentiate between
+      recursive and non-recursive columns of a recursive CTE.
+      TODO: this should be fixed.
+    */
+    bool pos_maybe_null= is_recursive ? true : holders[pos].get_maybe_null();
+
     /* Error's in 'new' will be detected after loop */
     types.push_back(new (thd_arg->mem_root)
                     Item_type_holder(thd_arg,
                                      item_tmp,
                                      holders[pos].type_handler(),
                                      &holders[pos]/*Type_all_attributes*/,
-                                     holders[pos].get_maybe_null()));
+                                     pos_maybe_null));
   }
   if (unlikely(thd_arg->is_fatal_error))
     DBUG_RETURN(true); // out of memory