json_populate_record issue - TupleDesc reference leak

When I tested json_populate_function in test http://stackoverflow.com/questions/7711432/how-to-set-value-of-composite-variable-field-using-dynamic-sql/28673097#28673097 I found a small issue

create type pt as (a int, b int);

postgres=# select json_populate_record('(10,20)'::pt, '{}');
WARNING:  TupleDesc reference leak: TupleDesc 0x7f10fcf41400 (567018,-1) still referenced
 json_populate_record
----------------------
 (10,20)
(1 row)