diff --git a/mysql-test/r/func_str.result b/mysql-test/r/func_str.result
index e0b4161a6a0..d6879a8e756 100644
--- a/mysql-test/r/func_str.result
+++ b/mysql-test/r/func_str.result
@@ -1095,6 +1095,18 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	system	NULL	NULL	NULL	NULL	0	const row not found
 Warnings:
 Note	1003	select decode('','zxcv') AS `enc` from `test`.`t1`
+drop table t1;
+create table t1 (a bigint not null)engine=myisam;
+insert into t1 set a = 1024*1024*1024*4;
+delete from t1 order by (inet_ntoa(a)) desc limit 10;
+drop table t1;
+create table t1 (a char(36) not null)engine=myisam;
+insert ignore into t1 set a = ' ';
+insert ignore into t1 set a = ' ';
+select * from t1 order by (oct(a));
+a
+
+
 drop table t1;
 End of 4.1 tests
 create table t1 (d decimal default null);
diff --git a/mysql-test/t/func_str.test b/mysql-test/t/func_str.test
index e04276fa305..1ca2bbfaf4c 100644
--- a/mysql-test/t/func_str.test
+++ b/mysql-test/t/func_str.test
@@ -738,6 +738,19 @@ explain extended select encode(f1,'zxcv') as 'enc' from t1;
 explain extended select decode(f1,'zxcv') as 'enc' from t1;
 drop table t1;
 
+#
+# Bug #31758 inet_ntoa, oct, crashes server with null + filesort 
+#
+create table t1 (a bigint not null)engine=myisam;
+insert into t1 set a = 1024*1024*1024*4;
+delete from t1 order by (inet_ntoa(a)) desc limit 10;
+drop table t1;
+create table t1 (a char(36) not null)engine=myisam;
+insert ignore into t1 set a = ' ';
+insert ignore into t1 set a = ' ';
+select * from t1 order by (oct(a));
+drop table t1;
+
 --echo End of 4.1 tests
 
 #
diff --git a/sql/item_strfunc.h b/sql/item_strfunc.h
index 04d1997e879..7607ebfc761 100644
--- a/sql/item_strfunc.h
+++ b/sql/item_strfunc.h
@@ -584,7 +584,8 @@ public:
   void fix_length_and_dec()
   {
     collation.set(default_charset());
-    max_length= 64;
+    max_length=64;
+    maybe_null= 1;
   }
 };
 
@@ -682,7 +683,7 @@ public:
     }
   String* val_str(String* str);
   const char *func_name() const { return "inet_ntoa"; }
-  void fix_length_and_dec() { decimals = 0; max_length=3*8+7; }
+  void fix_length_and_dec() { decimals = 0; max_length=3*8+7; maybe_null=1;}
 };
 
 class Item_func_quote :public Item_str_func