Why are .err files ignored by visit-file?

[Steven W. Orr]

emacs-21.2

I have a directory with two files in it: build.err and build.log

When I try to visit a file in this directory I hit the letter b
followed by space to complete. I expect the completion to take me to
the . after build. But it always completes on build.err  It's like
it's told to ignore .log files. 

Is there a way to turn this behavior off? I looked in the manuals but
found nothing.

TIA

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