diff --git a/.travis.yml b/.travis.yml
index d6832a5f0a6..709feaeaa37 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -121,12 +121,18 @@ install:
 
 - |
   echo "Installing Composer dependencies - PHP Unit, Parallel Lint, PHP CodeSniffer - for $TRAVIS_PHP_VERSION"
-  if [ "$TRAVIS_PHP_VERSION" = '5.6' ] || [ "$TRAVIS_PHP_VERSION" = '7.0' ] || [ "$TRAVIS_PHP_VERSION" = '7.1' ] || [ "$TRAVIS_PHP_VERSION" = '7.2' ]; then
+  if [ "$TRAVIS_PHP_VERSION" = '5.6' ]; then
     composer -n require phpunit/phpunit ^5 \
                         php-parallel-lint/php-parallel-lint ^1 \
                         php-parallel-lint/php-console-highlighter ^0 \
                         squizlabs/php_codesniffer ^3
   fi
+  if [ "$TRAVIS_PHP_VERSION" = '7.0' ] || [ "$TRAVIS_PHP_VERSION" = '7.1' ] || [ "$TRAVIS_PHP_VERSION" = '7.2' ]; then
+    composer -n require phpunit/phpunit ^6 \
+                        php-parallel-lint/php-parallel-lint ^1 \
+                        php-parallel-lint/php-console-highlighter ^0 \
+                        squizlabs/php_codesniffer ^3
+  fi
   if [ "$TRAVIS_PHP_VERSION" = '7.3' ] || [ "$TRAVIS_PHP_VERSION" = '7.4' ]; then
     composer -n require phpunit/phpunit ^7 \
                         php-parallel-lint/php-parallel-lint ^1.2 \