diff --git a/application/controllers/Logbook.php b/application/controllers/Logbook.php
index 414cf6d1c..fc529f452 100644
--- a/application/controllers/Logbook.php
+++ b/application/controllers/Logbook.php
@@ -221,7 +221,7 @@ class Logbook extends CI_Controller {
 			$return['latlng'] = $this->qralatlng($return['callsign_qra']);
 			$return['bearing'] = $this->bearing($return['callsign_qra'], $measurement_base, $station_id);
 		}
-		$return['callbook_source'] = $callbook['source'];
+		$return['callbook_source'] = $callbook['source'] ?? '';
 
 		echo json_encode($return, JSON_PRETTY_PRINT);