decr on Int64.MaxValue fails with "CLIENT_ERROR cannot increment or decrement non-numeric value"

[Sean]

Here's the repro on the largest unsigned 64-bit integer
18446744073709551615 with telnet on memcached 1.4.5

>set aad2ac07-2fd5-42bb-88b9-e7bae3b55f5b 0 200 20
18446744073709551615
STORED
>get aad2ac07-2fd5-42bb-88b9-e7bae3b55f5b
VALUE aad2ac07-2fd5-42bb-88b9-e7bae3b55f5b 0 20
18446744073709551615
END
>decr aad2ac07-2fd5-42bb-88b9-e7bae3b55f5b 100
CLIENT_ERROR cannot increment or decrement non-numeric value


Is this a known bug?