diff --git a/.travis.yml b/.travis.yml
index bcceed02..013169e8 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -4,7 +4,7 @@ node_js:
   - lts/*
 script:
   - npm run lint && npm run test
-  - npm install -g grunt npm@5.2 && grunt pre-build
+  - 'if [[ ${TRAVIS_PULL_REQUEST_BRANCH:-$TRAVIS_BRANCH} = "master" ]]; then npm install -g grunt npm@5.2 && grunt pre-build; fi'
 after_success:
   - openssl aes-256-cbc -K $encrypted_440d7f9a3c38_key -iv $encrypted_440d7f9a3c38_iv
     -in .snapcraft/travis_snapcraft.cfg -out .snapcraft/snapcraft.cfg -d