diff --git a/src/widget.ts b/src/widget.ts
index 390a005..e1ffbd3 100644
--- a/src/widget.ts
+++ b/src/widget.ts
@@ -104,7 +104,7 @@ export class HtmlViewer extends Widget {
         if (!cm) {
             return;
         }
-        let url = this.node.baseURI.replace("/lab", "/files/") + this.context.path;
+        let url = this.node.baseURI.replace(/\/lab.*/, "/files/") + this.context.path;
         this._html.setAttribute('src', url);
     }