Another Typhoeus VCR failure

Gemfile

gem "typhoeus", git: "https://github.com/typhoeus/typhoeus.git",
                ref: "8e815cdf4fed2322947e2338d6f5b084c820a70b"
gem "vcr"
gem "rspec"

vcr_spec.rb

require "bundler/setup"
require "typhoeus"
require "vcr"

VCR.configure do |config|
  config.cassette_library_dir = "vcr_cassettes"
  config.hook_into              :typhoeus
end

describe VCR do
  it "should work with callbacks registered after the request is queued" do
    VCR.use_cassette("late_callbacks") do
      hydra   = Typhoeus::Hydra.new
      request = Typhoeus::Request.new("http://xkcd.com/")
      success = false

      hydra.queue(request)
      request.on_success do |_|
        success = true
      end
      hydra.run

      expect(success).to be_true
    end
  end
end

# $ rspec vcr_spec.rb 
# .
# 
# Finished in 0.21526 seconds
# 1 example, 0 failures
# $ rspec vcr_spec.rb 
# F
# 
# Failures:
# 
#   1) VCR should work with callbacks registered after the request is queued
#      Failure/Error: expect(success).to be_true
#        expected: true value
#             got: false
#      # ./vcr_spec.rb:23:in `block (3 levels) in <top (required)>'
#      # ./vcr_spec.rb:12:in `block (2 levels) in <top (required)>'
# 
# Finished in 0.0094 seconds
# 1 example, 1 failure
# 
# Failed examples:
# 
# rspec ./vcr_spec.rb:11 # VCR should work with callbacks registered after the request is queued