diff --git a/mysql-test/r/null.result b/mysql-test/r/null.result
index 0d012e283b5..fcaaeb2192f 100644
--- a/mysql-test/r/null.result
+++ b/mysql-test/r/null.result
@@ -1572,5 +1572,22 @@ SELECT * FROM t1 WHERE NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(N
 i
 DROP TABLE t1;
 #
+# MDEV-10236 Where expression with NOT function gives incorrect result
+#
+CREATE TABLE t1 (c1 INT);
+INSERT INTO t1 VALUES (1),(2),(3);
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE ((c1 IS NOT NULL) >= (NOT TRUE)) IS NOT NULL;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	3	100.00	Using where
+Warnings:
+Note	1003	select `test`.`t1`.`c1` AS `c1` from `test`.`t1` where (((`test`.`t1`.`c1` is not null) >= <cache>((not(1)))) is not null)
+SELECT * FROM t1 WHERE ((c1 IS NOT NULL) >= (NOT TRUE)) IS NOT NULL;
+c1
+1
+2
+3
+DROP TABLE t1;
+#
 # End of 10.1 tests
 #
diff --git a/mysql-test/t/null.test b/mysql-test/t/null.test
index a5db4442183..84b3f069683 100644
--- a/mysql-test/t/null.test
+++ b/mysql-test/t/null.test
@@ -1007,6 +1007,17 @@ SELECT * FROM t1 WHERE NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(NULLIF(N
 DROP TABLE t1;
 
 
+--echo #
+--echo # MDEV-10236 Where expression with NOT function gives incorrect result
+--echo #
+CREATE TABLE t1 (c1 INT);
+INSERT INTO t1 VALUES (1),(2),(3);
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE ((c1 IS NOT NULL) >= (NOT TRUE)) IS NOT NULL;
+SELECT * FROM t1 WHERE ((c1 IS NOT NULL) >= (NOT TRUE)) IS NOT NULL;
+DROP TABLE t1;
+
+
 --echo #
 --echo # End of 10.1 tests
 --echo #
diff --git a/sql/item.h b/sql/item.h
index bef57c4a967..93da3985d4c 100644
--- a/sql/item.h
+++ b/sql/item.h
@@ -5050,7 +5050,7 @@ public:
   bool basic_const_item() const
   { return MY_TEST(example && example->basic_const_item()); }
   virtual void clear() { null_value= TRUE; value_cached= FALSE; }
-  bool is_null() { return null_value; }
+  bool is_null() { return !has_value(); }
   virtual bool is_expensive()
   {
     if (value_cached)