diff --git a/src/viewer.js b/src/viewer.js
index 2ddc6b1349..abdfd1c25b 100644
--- a/src/viewer.js
+++ b/src/viewer.js
@@ -21,6 +21,8 @@ if (OCA.Viewer) {
 		theme: 'default',
 		canCompare: true,
 	})
+} else {
+	console.error('Unable to register viewer handler')
 }
 
 autoSetupBuiltInCodeServerIfNeeded()