Weird behaviour by the Parser params

gistfile1.hs

params :: Parser Params
params = do
    ps <- takeWhile (notInClass ":\r") `sepBy` space

*Tob.Parser> maybeResult $ parse params $ T.pack "foo bar xyz:"
Just ["foo bar xyz"]
*Tob.Parser> maybeResult $ parse params $ T.pack "foo bar xyz :"
Just ["foo bar xyz "]
*Tob.Parser> maybeResult $ parse params $ T.pack "foo bar xyz \r"
Nothing
*Tob.Parser> maybeResult $ parse params $ T.pack "foo bar xyz\r"
Nothing

Behaviour I want:

> maybeResult $ parse params $ T.pack "foo bar xyz :"
Just ["foo", "bar", "xyz"]
> maybeResult $ parse params $ T.pack "foo bar xyz\r"
Just ["foo", "bar", "xyz"]

How can this NOT work? o.o

*Tob.Parser> let p = takeWhile (/= '\n') `sepBy` space
*Tob.Parser> maybeResult $ parse p $ T.pack "hahah ahahah ahahah\n"
Nothing