incr/decr do not return cas when :extended => true passed in, cas always null

I tried this on 1.3.3, but it might be broken in earlier releases as well....

docs say this syntax:
val, cas = c.incr("foo", :extended => true)

what I tried:
client.set(key, 100)
doc, cas = client.incr(key, :extended => true)
doc, cas = client.incr(key, 5, :extended => true)
doc, cas = client.incr(key, {:delta => 5, :extended => true})

doc, cas = client.decr(key, :extended => true)
doc, cas = client.decr(key, 5, :extended => true)
doc, cas = client.decr(key, {:delta => 5, :extended => true})

cas is always null in all 6 tests