Why is the Signature section of my Haddock generated documentation home page empty?

I'm generating documentation for my Haskell library using:

stack haddock --no-haddock-deps

And the resultant index.html page has an empty Signatures section.

Why is the Signatures section empty?

Thanks to the comment from @sjakobi, I now understand that the Signatures section is populated with a module's Backpack signatures, which my module lacks. So, I shouldn't expect any content in that section.