Can't find the 'libpq-fe.h header when trying to install pg gem

Question

I am using the Ruby on Rails 3.1 pre version. I like to use PostgreSQL, but the problem is installing the pg gem. It gives me the following error:

Answer 1

I had this issue with Postgresql 9.6. I was able to fix it by doing:

brew upgrade postgresql@9.6
brew link postgresql@9.6 --force
gem install pg