diff --git a/mysql-test/r/ctype_utf8.result b/mysql-test/r/ctype_utf8.result
index a98beb36ef1..748361d3178 100644
--- a/mysql-test/r/ctype_utf8.result
+++ b/mysql-test/r/ctype_utf8.result
@@ -1001,6 +1001,9 @@ set @a:='bar';
 execute my_stmt using @a;
 a	b
 bar	kostja
+set @a:=NULL;
+execute my_stmt using @a;
+a	b
 drop table t1;
 CREATE TABLE t1 (
 a varchar(255) NOT NULL default '',
diff --git a/mysql-test/t/ctype_utf8.test b/mysql-test/t/ctype_utf8.test
index ede9665941a..e6342777839 100644
--- a/mysql-test/t/ctype_utf8.test
+++ b/mysql-test/t/ctype_utf8.test
@@ -840,6 +840,8 @@ insert into t1 values ('bar','kostja');
 prepare my_stmt from "select * from t1 where a=?";
 set @a:='bar';
 execute my_stmt using @a;
+set @a:=NULL;
+execute my_stmt using @a;
 drop table t1;
 
 
diff --git a/sql/item.cc b/sql/item.cc
index 53640c4e44a..2d4f9138a51 100644
--- a/sql/item.cc
+++ b/sql/item.cc
@@ -290,7 +290,13 @@ Item *Item_param::safe_charset_converter(CHARSET_INFO *tocs)
   {
     Item_string *conv;
     uint conv_errors;
-    String tmp, cstr, *ostr= val_str(&tmp);
+    char buf[MAX_FIELD_WIDTH];
+    String tmp(buf, sizeof(buf), &my_charset_bin);
+    String cstr, *ostr= val_str(&tmp);
+    /*
+      As safe_charset_converter is not executed for
+      a parameter bound to NULL, ostr should never be 0.
+    */
     cstr.copy(ostr->ptr(), ostr->length(), ostr->charset(), tocs, &conv_errors);
     if (conv_errors || !(conv= new Item_string(cstr.ptr(), cstr.length(),
                                                cstr.charset(),