How to fix Linux filename tab autocomplete that is appending a space instead of trailing slash on directories?

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http://unix.stackexchange.com – For some strange reason my filename autocomplete is behaving differently than normal. Given the following file structure ./foobar/file.txt, if I want to delete file.txt, I type rm foob<TAB><TAB> and let the command line autocomplete the filename out to rm foobar/file.txt. But right now, after hitting the first <TAB> my command gets autocompleted to rm foobar (with a space after foobar). Is it possible that I accidentally changed it to this behavior? How can I change it back? (HowTos)