diff --git a/tests/phpunit/includes/abstract-testcase.php b/tests/phpunit/includes/abstract-testcase.php
index 39aa893295..4dbbea959f 100644
--- a/tests/phpunit/includes/abstract-testcase.php
+++ b/tests/phpunit/includes/abstract-testcase.php
@@ -181,8 +181,8 @@ abstract class WP_UnitTestCase_Base extends PHPUnit\Framework\TestCase {
 	/**
 	 * Allow tests to be skipped on some automated runs.
 	 *
-	 * For test runs on Travis/GitHub Actions for something other than trunk/master, we want to skip tests that
-	 * only need to run for master.
+	 * For test runs on Travis/GitHub Actions for something other than trunk/master,
+	 * we want to skip tests that only need to run for master.
 	 */
 	public function skipOnAutomatedBranches() {
 		// https://docs.travis-ci.com/user/environment-variables/#Default-Environment-Variables
@@ -193,14 +193,14 @@ abstract class WP_UnitTestCase_Base extends PHPUnit\Framework\TestCase {
 		$github_event_name = getenv( 'GITHUB_EVENT_NAME' );
 		$github_ref        = getenv( 'GITHUB_REF' );
 
-		if ( 'false' !== $github_event_name ) {
+		if ( $github_event_name && 'false' !== $github_event_name ) {
 			// We're on GitHub Actions.
 			$skipped = array( 'pull_request', 'pull_request_target' );
 
 			if ( in_array( $github_event_name, $skipped, true ) || 'refs/heads/master' !== $github_ref ) {
 				$this->markTestSkipped( 'For automated test runs, this test is only run on trunk/master' );
 			}
-		} elseif ( 'false' !== $travis_branch ) {
+		} elseif ( $travis_branch && 'false' !== $travis_branch ) {
 			// We're on Travis CI.
 			if ( 'master' !== $travis_branch || 'false' !== $travis_pull_request ) {
 				$this->markTestSkipped( 'For automated test runs, this test is only run on trunk/master' );