haskell-indent-mode does not complete function name when using Unicode Symbols

For example, I have:

```
main :: IO()
```

When I on the second line twice, the function name `main` is completed IF I use ASCII symbols above. However, if I use Unicode symbols:

```
main ∷ IO ()
```

That functionality won't work. Also, If I break the argument list to multiple lines:

```
f :: a
-> b
```

This functionality does not work