.travis.yml in iri-0.4.2 vs .travis.yml in iri-0.4.3

@@ -5,10 +5,10 @@
 branches:
   only:
     - master
 install:
   - travis_retry bundle update
-  - gem install pdd
+  - gem install pdd -v 0.20.5
 script:
   - pdd -f /dev/null
   - bundle exec rake
 after_success:
   - "bash <(curl -s https://codecov.io/bash)"