Initializing the gocardless_pro client (2.9.0) with faraday 0.16.2 raised undefined method 'each' for nil:NilClass (NoMethodError) from faraday's options.rb during Faraday.new. It worked on faraday 0.15.4. The reporter later found it also worked on faraday 0.17.0 — the bug was in faraday 0.16.x itself, not the GoCardless version lock.

Not a GoCardless bug — faraday 0.16.x had the regression. The reporter confirmed 0.17.0 works, and the issue was closed as superseded. Fix: upgrade faraday to 0.17.0+ (a maintainer suggested the gem require ~> 0.17). Downgrading to 0.15.4 also works as a stopgap. Source: https://github.com/gocardless/gocardless-pro-ruby/issues/53