What steps will reproduce the problem?

http://play.golang.org/p/yti7xDJCCX

What is the expected output?

[main.go] <nil>
[main.go] <nil>

What do you see instead?

[main.go] <nil>
[] <nil>

Which compiler are you using (5g, 6g, 8g, gccgo)?

6g

Which operating system are you using?

OS X and Linux

Which version are you using?  (run 'go version')

go version go1.1 darwin/amd64

Please provide any additional information below.

The same issue occurs when calling File.Readdir more than once or combining calls of
File.Readdirnames and File.Readdir.