diff --git a/tests/phpunit/tests/db.php b/tests/phpunit/tests/db.php
index 3e06afcc1bf2c..fc2413751ff47 100644
--- a/tests/phpunit/tests/db.php
+++ b/tests/phpunit/tests/db.php
@@ -296,7 +296,7 @@ public function test_set_sql_mode() {
 		$check_new_modes = $wpdb->get_var( 'SELECT @@SESSION.sql_mode;' );
 		$this->assertSameSets( $new_modes, explode( ',', $check_new_modes ) );
 
-		$wpdb->set_sql_mode( explode( ',', $current_modes ) );
+		$wpdb->set_sql_mode( empty( $current_modes ) ? '' : explode( ',', $current_modes ) );
 	}
 
 	/**