diff --git a/BlueMapCore/src/main/webroot/js/libs/BlueMap.js b/BlueMapCore/src/main/webroot/js/libs/BlueMap.js
index b0fea56e..e736a919 100644
--- a/BlueMapCore/src/main/webroot/js/libs/BlueMap.js
+++ b/BlueMapCore/src/main/webroot/js/libs/BlueMap.js
@@ -109,7 +109,7 @@ export default class BlueMap {
 			await this.ui.load();
 			this.start();
 		}).catch(error => {
-			this.onLoadError("Initialization: " + error.toString());
+			this.onLoadError("Initialization: " + (error ? error.toString() : "unknown"));
 		});
 	}