diff --git a/.travis.yml b/.travis.yml
index 8f4591123..5ee497916 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -68,6 +68,9 @@ before_script:
   # PHPUnit 6 is required when running tests on PHP 7.x.
   - test ${TEST_SUITE} == "PHP_CodeSniffer" || test ${TRAVIS_PHP_VERSION:0:3} == "5.6" || composer require --dev phpunit/phpunit:~6 --update-with-dependencies --working-dir=$DRUPAL_DIR
 
+  # PHPUnit 7 is required when running tests Drupal 9.
+  - test ${TEST_SUITE:0:1} == "9"  || composer require --dev phpunit/phpunit:~7 --update-with-dependencies --working-dir=$DRUPAL_DIR
+
   # Start a web server on port 8888 in the background.
   - test ${TEST_SUITE} == "PHP_CodeSniffer" || nohup php -S localhost:8888 --docroot $DRUPAL_DIR > /dev/null 2>&1 &