diff --git a/tests/phpunit/includes/bootstrap.php b/tests/phpunit/includes/bootstrap.php
index 0390d62312..23faca64e5 100644
--- a/tests/phpunit/includes/bootstrap.php
+++ b/tests/phpunit/includes/bootstrap.php
@@ -33,6 +33,7 @@ if ( ! is_readable( $config_file_path ) ) {
 	echo "ERROR: wp-tests-config.php is missing! Please use wp-tests-config-sample.php to create a config file.\n";
 	exit( 1 );
 }
+
 require_once $config_file_path;
 require_once dirname( __FILE__ ) . '/functions.php';
 
@@ -45,6 +46,11 @@ if ( version_compare( tests_get_phpunit_version(), '8.0', '>=' ) ) {
 	exit( 1 );
 }
 
+if ( defined( 'WP_RUN_CORE_TESTS' ) && WP_RUN_CORE_TESTS && ! is_dir( ABSPATH ) ) {
+	echo "ERROR: The /build/ directory is missing! Please run `grunt build` prior to running PHPUnit.\n";
+	exit( 1 );
+}
+
 tests_reset__SERVER();
 
 define( 'WP_TESTS_TABLE_PREFIX', $table_prefix );