diff --git a/mysql-test/r/subselect_sj2_mat.result b/mysql-test/r/subselect_sj2_mat.result
index 4e75aee24a2..202e6cc4b9e 100644
--- a/mysql-test/r/subselect_sj2_mat.result
+++ b/mysql-test/r/subselect_sj2_mat.result
@@ -1556,3 +1556,26 @@ i1
 DROP TABLE t1,t2,t3;
 set join_cache_level= @save_join_cache_level;
 set optimizer_switch=@save_optimizer_switch;
+#
+# mdev-7791: materialization of a semi-join subquery +
+#            RAND() in WHERE
+#            (materialized table is accessed last)
+#
+set @save_optimizer_switch=@@optimizer_switch;
+set optimizer_switch='materialization=on';
+create table t1(i int);
+insert into t1 values (1), (2), (3), (7), (9), (10);
+create table t2(i int);
+insert into t2 values (1), (2), (3), (4), (5), (6), (7), (8), (9), (10);
+select * from t1 where (rand() < 0) and i in (select i from t2);
+i
+explain extended
+select * from t1 where (rand() < 0) and i in (select i from t2);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	6	100.00	Using where
+1	PRIMARY	<subquery2>	eq_ref	distinct_key	distinct_key	4	func	1	100.00	
+2	MATERIALIZED	t2	ALL	NULL	NULL	NULL	NULL	10	100.00	
+Warnings:
+Note	1003	select `test`.`t1`.`i` AS `i` from `test`.`t1` semi join (`test`.`t2`) where ((rand() < 0))
+drop table t1,t2;
+set optimizer_switch=@save_optimizer_switch;
diff --git a/mysql-test/t/subselect_sj2_mat.test b/mysql-test/t/subselect_sj2_mat.test
index 61d9b09edff..0f2892ae2dc 100644
--- a/mysql-test/t/subselect_sj2_mat.test
+++ b/mysql-test/t/subselect_sj2_mat.test
@@ -263,3 +263,23 @@ DROP TABLE t1,t2,t3;
 set join_cache_level= @save_join_cache_level;
 set optimizer_switch=@save_optimizer_switch;
 
+--echo #
+--echo # mdev-7791: materialization of a semi-join subquery +
+--echo #            RAND() in WHERE
+--echo #            (materialized table is accessed last)
+--echo #
+
+set @save_optimizer_switch=@@optimizer_switch;
+set optimizer_switch='materialization=on';
+
+create table t1(i int);
+insert into t1 values (1), (2), (3), (7), (9), (10);
+create table t2(i int);
+insert into t2 values (1), (2), (3), (4), (5), (6), (7), (8), (9), (10);
+
+select * from t1 where (rand() < 0) and i in (select i from t2);
+explain extended
+select * from t1 where (rand() < 0) and i in (select i from t2);
+
+drop table t1,t2;
+set optimizer_switch=@save_optimizer_switch;
diff --git a/sql/sql_select.cc b/sql/sql_select.cc
index 09e6ece7807..bad57aeac87 100644
--- a/sql/sql_select.cc
+++ b/sql/sql_select.cc
@@ -8761,12 +8761,20 @@ make_join_select(JOIN *join,SQL_SELECT *select,COND *cond)
     /*
       Step #2: Extract WHERE/ON parts
     */
+    uint i;
+    for (i= join->top_join_tab_count - 1; i >= join->const_tables; i--)
+    {
+      if (!join->join_tab[i].bush_children)
+        break;
+    }
+    uint last_top_base_tab_idx= i;
+
     table_map save_used_tables= 0;
     used_tables=((select->const_tables=join->const_table_map) |
 		 OUTER_REF_TABLE_BIT | RAND_TABLE_BIT);
     JOIN_TAB *tab;
     table_map current_map;
-    uint i= join->const_tables;
+    i= join->const_tables;
     for (tab= first_depth_first_tab(join); tab;
          tab= next_depth_first_tab(join, tab), i++)
     {
@@ -8804,7 +8812,7 @@ make_join_select(JOIN *join,SQL_SELECT *select,COND *cond)
 	Following force including random expression in last table condition.
 	It solve problem with select like SELECT * FROM t1 WHERE rand() > 0.5
       */
-      if (tab == join->join_tab + join->top_join_tab_count - 1)
+      if (tab == join->join_tab + last_top_base_tab_idx)
         current_map|= RAND_TABLE_BIT;
       used_tables|=current_map;
 
@@ -8843,10 +8851,10 @@ make_join_select(JOIN *join,SQL_SELECT *select,COND *cond)
           save_used_tables= 0;
         }
         else
-         {
-	  tmp= make_cond_for_table(thd, cond, used_tables, current_map, i,
+        {
+          tmp= make_cond_for_table(thd, cond, used_tables, current_map, i,
                                    FALSE, FALSE);
-         }
+        }
         /* Add conditions added by add_not_null_conds(). */
         if (tab->select_cond)
           add_cond_and_fix(thd, &tmp, tab->select_cond);