Gemfile in neo4j-8.1.5 vs Gemfile in neo4j-8.2.1

@@ -2,12 +2,14 @@
 
 gemspec
 
 # gem 'neo4j-core', github: 'neo4jrb/neo4j-core', branch: 'master' if ENV['CI']
 
-if branch = ENV['TRAVIS_BRANCH']
-  if `curl --head https://github.com/#{ENV['TRAVIS_REPO_SLUG']}-core/tree/#{branch} | head -1` =~ /200 OK/
-    gem 'neo4j-core', github: "#{ENV['TRAVIS_REPO_SLUG']}-core", branch:  branch
+branch = ENV['TRAVIS_PULL_REQUEST_BRANCH'] || ENV['TRAVIS_BRANCH']
+slug = ENV['TRAVIS_PULL_REQUEST_SLUG'] || ENV['TRAVIS_REPO_SLUG']
+if branch
+  if `curl --head https://github.com/#{slug}-core/tree/#{branch} | head -1` =~ /200 OK/
+    gem 'neo4j-core', github: "#{slug}-core", branch: branch
   else
     gem 'neo4j-core', github: 'neo4jrb/neo4j-core', branch: 'master'
   end
 elsif ENV['USE_LOCAL_CORE']
   gem 'neo4j-core', path: '../neo4j-core'