diff --git a/includes/extensions/lightbox-entry/class-gravityview-lightbox-entry.php b/includes/extensions/lightbox-entry/class-gravityview-lightbox-entry.php
index eb5bbbadf..a661e7441 100644
--- a/includes/extensions/lightbox-entry/class-gravityview-lightbox-entry.php
+++ b/includes/extensions/lightbox-entry/class-gravityview-lightbox-entry.php
@@ -398,7 +398,7 @@ private function process_duplicate_entry() {
 	public function process_gravity_forms_form_submission( $response ) {
 		$rest_endpoint = $this->get_rest_endpoint_from_request();
 
-		if ( 1 === (int) ( $_REQUEST['gform_submit'] ?? 0 ) && $rest_endpoint ) {
+		if ( array_key_exists( 'gform_submit', $_REQUEST ) && $rest_endpoint ) {
 			header( 'Content-Type: text/html' );
 		}