Editing cabal file rejected due to unfixable syntax-error

I tried adding an upper bound `primitive < 0.5` (since compilation of `hashtables-1.0.0.0` fails due to the `memsetByteArray` operation which was removed in `primitive-0.5`) via

http://hackage.haskell.org/package/hashtables-1.0.0.0/hashtables.cabal/edit

But then Hackage server complains about

```
New parse warning: hashtables-1.0.0.0.cabal: Unexpected section 'cpp-options' on line 173
```

which is due to the line

```
cpp-options = -DUNSAFETRICKS
```

fixing the `=` into `:` however let's Hackage complain that

```
Cannot change build information (just the dependency version constraints)
```

...so is there anything that can be done?

/cc @gregorycollins