diff --git a/.travis.yml b/.travis.yml
index 47dd4b9f..02afd6a7 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -3,7 +3,8 @@ language: php
 dist: trusty
 
 php:
-  - 5.5
+  - 5.4
+  - 5.5.9
   - 5.6
   - 7.0
   - 7.1
@@ -28,6 +29,7 @@ cache:
     - "$HOME/.composer/cache"
 
 before_script:
+  - if find . -name "*.php" ! -path "*/vendor/*" -exec php -l {} 2>&1 \; | grep "syntax error, unexpected"; then exit 1; fi
   - if [[ "$SETUP" = "basic" ]]; then composer install --no-interaction --prefer-dist; fi
   - if [[ "$SETUP" = "lowest" ]]; then travis_retry composer update --prefer-dist --no-interaction --prefer-lowest --prefer-stable; fi
   - if [[ $TRAVIS_PHP_VERSION = "5.6" && "$SETUP" = "basic" ]]; then PHPUNIT_FLAGS="--coverage-clover build/logs/clover.xml"; fi