diff --git a/mysql-test/main/natural_sort_key.result b/mysql-test/main/natural_sort_key.result
index a99fa7a71b8..10adc7acef3 100644
--- a/mysql-test/main/natural_sort_key.result
+++ b/mysql-test/main/natural_sort_key.result
@@ -190,3 +190,16 @@ pic120              	pic2120
 pic121              	pic2121
 pic02000            	pic32000
 tom                 	tom
+create table t (a varchar(8), b varchar(8) as (natural_sort_key(a)));
+insert into t (a) values ('a2'),(NULL),('a11');
+select * from t order by b;
+a	b
+NULL	NULL
+a2	a02
+a11	a111
+select a, b from t order by b;
+a	b
+NULL	NULL
+a2	a02
+a11	a111
+drop table t;
diff --git a/mysql-test/main/natural_sort_key.test b/mysql-test/main/natural_sort_key.test
index dda25c9e1f8..4f4e2b0e05e 100644
--- a/mysql-test/main/natural_sort_key.test
+++ b/mysql-test/main/natural_sort_key.test
@@ -86,3 +86,10 @@ SELECT RPAD(val,20,' ') value, NATURAL_SORT_KEY(val) FROM
 ('a01b3')
 )AS data ORDER BY 2,1;
 
+# MDEV-27686 (null value indicator not always reset)
+create table t (a varchar(8), b varchar(8) as (natural_sort_key(a)));
+insert into t (a) values ('a2'),(NULL),('a11');
+select * from t order by b;
+select a, b from t order by b;
+drop table t;
+
diff --git a/sql/item_strfunc.cc b/sql/item_strfunc.cc
index 60e2d297459..f43115fef54 100644
--- a/sql/item_strfunc.cc
+++ b/sql/item_strfunc.cc
@@ -5682,7 +5682,7 @@ String *Item_func_natural_sort_key::val_str(String *out)
     if (tmp.copy(out, cs, &errs) || out->copy(tmp))
       goto error_exit;
   }
-
+  null_value= false;
   return out;
 
 error_exit: