diff --git a/mysql-test/r/func_in.result b/mysql-test/r/func_in.result
index b88e5a66f96..6578af7cd8b 100644
--- a/mysql-test/r/func_in.result
+++ b/mysql-test/r/func_in.result
@@ -202,6 +202,14 @@ select count(*) from t1 where id not in (1,2);
 count(*)
 1
 drop table t1;
+DROP TABLE IF EXISTS t1;
+CREATE TABLE t1 SELECT 1 IN (2, NULL);
+SELECT should return NULL.
+SELECT * FROM t1;
+1 IN (2, NULL)
+NULL
+DROP TABLE t1;
+End of 4.1 tests
 CREATE TABLE t1 (a int PRIMARY KEY);
 INSERT INTO t1 VALUES (44), (45), (46);
 SELECT * FROM t1 WHERE a IN (45);
@@ -343,6 +351,7 @@ some_id
 1
 2
 drop table t1;
+End of 5.0 tests
 create table t1(f1 char(1));
 insert into t1 values ('a'),('b'),('1');
 select f1 from t1 where f1 in ('a',1);
@@ -411,3 +420,4 @@ explain select f2 from t2 where f2 in (1,'b');
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t2	index	NULL	t2f2	5	NULL	3	Using where; Using index
 drop table t1, t2;
+End of 5.1 tests
diff --git a/mysql-test/r/func_str.result b/mysql-test/r/func_str.result
index 733cb5ca5f0..60b9763124f 100644
--- a/mysql-test/r/func_str.result
+++ b/mysql-test/r/func_str.result
@@ -1148,6 +1148,20 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 Warnings:
 Note	1003	select `test`.`t1`.`code` AS `code`,`test`.`t2`.`id` AS `id` from `test`.`t1` join `test`.`t2` where ((`test`.`t1`.`code` = _latin1'a12') and (length(`test`.`t1`.`code`) = 5))
 DROP TABLE t1,t2;
+SET @orig_sql_mode = @@SQL_MODE;
+SET SQL_MODE=traditional;
+SELECT CHAR(0xff,0x8f USING utf8);
+CHAR(0xff,0x8f USING utf8)
+NULL
+Warnings:
+Error	1300	Invalid utf8 character string: 'FF8F'
+SELECT CHAR(0xff,0x8f USING utf8) IS NULL;
+CHAR(0xff,0x8f USING utf8) IS NULL
+1
+Warnings:
+Error	1300	Invalid utf8 character string: 'FF8F'
+SET SQL_MODE=@orig_sql_mode;
+End of 5.0 tests
 select locate('he','hello',-2);
 locate('he','hello',-2)
 0
@@ -1903,4 +1917,4 @@ Warnings:
 Error	1292	Truncated incorrect DECIMAL value: ''
 Error	1292	Truncated incorrect DECIMAL value: ''
 Warning	1301	Result of lpad() was larger than max_allowed_packet (1048576) - truncated
-End of 5.0 tests
+End of 5.1 tests
diff --git a/mysql-test/t/func_in.test b/mysql-test/t/func_in.test
index 906747c2f78..ee344d0958b 100644
--- a/mysql-test/t/func_in.test
+++ b/mysql-test/t/func_in.test
@@ -109,7 +109,28 @@ select count(*) from t1 where id not in (1);
 select count(*) from t1 where id not in (1,2);
 drop table t1;
 
-# End of 4.1 tests
+
+#
+# BUG#17047: CHAR() and IN() can return NULL without signaling NULL
+# result
+#
+# The problem was in the IN() function that ignored maybe_null flags
+# of all arguments except the first (the one _before_ the IN
+# keyword, '1' in the test case below).
+#
+--disable_warnings
+DROP TABLE IF EXISTS t1;
+--enable_warnings
+
+CREATE TABLE t1 SELECT 1 IN (2, NULL);
+--echo SELECT should return NULL.
+SELECT * FROM t1;
+
+DROP TABLE t1;
+
+
+--echo End of 4.1 tests
+
 
 #
 # Bug #11885: WHERE condition with NOT IN (one element)          
@@ -233,6 +254,10 @@ select some_id from t1 where some_id not in(-4,-1,-4);
 select some_id from t1 where some_id not in(-4,-1,3423534,2342342);
 drop table t1;
 
+
+--echo End of 5.0 tests
+
+
 #
 # Bug#18360: Type aggregation for IN and CASE may lead to a wrong result 
 #
@@ -256,3 +281,6 @@ explain select f2 from t2 where f2 in ('a','b');
 select f2 from t2 where f2 in (1,'b');
 explain select f2 from t2 where f2 in (1,'b');
 drop table t1, t2;
+
+
+--echo End of 5.1 tests
diff --git a/mysql-test/t/func_str.test b/mysql-test/t/func_str.test
index 9622de96143..4a9a6d3e1c6 100644
--- a/mysql-test/t/func_str.test
+++ b/mysql-test/t/func_str.test
@@ -780,6 +780,23 @@ SELECT * FROM t1 INNER JOIN t2 ON code=id
 
 DROP TABLE t1,t2;
 
+
+#
+# BUG#17047: CHAR() and IN() can return NULL without signaling NULL
+# result
+#
+SET @orig_sql_mode = @@SQL_MODE;
+SET SQL_MODE=traditional;
+
+SELECT CHAR(0xff,0x8f USING utf8);
+SELECT CHAR(0xff,0x8f USING utf8) IS NULL;
+
+SET SQL_MODE=@orig_sql_mode;
+
+
+--echo End of 5.0 tests
+
+
 #
 # Bug #10963
 # 4294967296 18446744073709551616
@@ -969,4 +986,5 @@ select lpad('hello', 18446744073709551616, '1');
 select lpad('hello', -18446744073709551617, '1');
 select lpad('hello', 18446744073709551617, '1');
 
---echo End of 5.0 tests
+
+--echo End of 5.1 tests
diff --git a/sql/item_cmpfunc.cc b/sql/item_cmpfunc.cc
index 691715c3bff..79d37c50030 100644
--- a/sql/item_cmpfunc.cc
+++ b/sql/item_cmpfunc.cc
@@ -2519,7 +2519,6 @@ void Item_func_in::fix_length_and_dec()
       }
     }
   }
-  maybe_null= args[0]->maybe_null;
   max_length= 1;
 }
 
diff --git a/sql/item_strfunc.cc b/sql/item_strfunc.cc
index 7237b4e37ae..a8e996a0ec3 100644
--- a/sql/item_strfunc.cc
+++ b/sql/item_strfunc.cc
@@ -80,6 +80,20 @@ String *Item_str_func::check_well_formed_result(String *str)
 }
 
 
+bool Item_str_func::fix_fields(THD *thd, Item **ref)
+{
+  bool res= Item_func::fix_fields(thd, ref);
+  /*
+    In Item_str_func::check_well_formed_result() we may set null_value
+    flag on the same condition as in test() below.
+  */
+  maybe_null= (maybe_null ||
+               test(thd->variables.sql_mode &
+                    (MODE_STRICT_TRANS_TABLES | MODE_STRICT_ALL_TABLES)));
+  return res;
+}
+
+
 my_decimal *Item_str_func::val_decimal(my_decimal *decimal_value)
 {
   DBUG_ASSERT(fixed == 1);
diff --git a/sql/item_strfunc.h b/sql/item_strfunc.h
index 2adccd212b3..9dfd9b37536 100644
--- a/sql/item_strfunc.h
+++ b/sql/item_strfunc.h
@@ -37,6 +37,7 @@ public:
   enum Item_result result_type () const { return STRING_RESULT; }
   void left_right_max_length();
   String *check_well_formed_result(String *str);
+  bool fix_fields(THD *thd, Item **ref);
 };
 
 class Item_func_md5 :public Item_str_func
@@ -530,9 +531,8 @@ public:
   { collation.set(cs); }  
   String *val_str(String *);
   void fix_length_and_dec() 
-  { 
-    maybe_null=0;
-    max_length=arg_count * collation.collation->mbmaxlen;
+  {
+    max_length= arg_count * collation.collation->mbmaxlen;
   }
   const char *func_name() const { return "char"; }
 };