diff --git a/lib/content-services/src/lib/viewer/components/alfresco-viewer.component.ts b/lib/content-services/src/lib/viewer/components/alfresco-viewer.component.ts
index 48a887bba2..17f40431dc 100644
--- a/lib/content-services/src/lib/viewer/components/alfresco-viewer.component.ts
+++ b/lib/content-services/src/lib/viewer/components/alfresco-viewer.component.ts
@@ -188,7 +188,7 @@ export class AlfrescoViewerComponent implements OnChanges, OnInit {
 
     /** Change the close button position Right/Left */
     @Input()
-    closeButtonPosition = CloseButtonPosition.Left;
+    closeButtonPosition: CloseButtonPosition = CloseButtonPosition.Left;
 
     /** The template for the right sidebar. The template context contains the loaded node data. */
     @Input()