Make vimdiff display different lines as different lines (not partially different)

vimdiff has an annoying habit of displaying two almost-completely-different lines as the same partially-different line just because they share a character in common at the beginning or end. For example: foo.txt contains: The quick brown fox jumps over the lazy dog. bar.txt contains: This is a completely different line. vimdiff foo.txt bar.txt displays these two lines side-by-side with everything but the Th at the beginning highlighted. Is there a way to disable this behaviour and just display different lines as being different lines?