diff --git a/packages/jupyterlab-kite/src/connection_manager.ts b/packages/jupyterlab-kite/src/connection_manager.ts
index 22b0576..98d8e49 100644
--- a/packages/jupyterlab-kite/src/connection_manager.ts
+++ b/packages/jupyterlab-kite/src/connection_manager.ts
@@ -302,7 +302,7 @@ export namespace DocumentConnectionManager {
 
     return {
       base: baseUri,
-      document: URLExt.join(baseUri, virtual_document.uri),
+      document: URLExt.join(baseUri, virtual_document.uri).replace("file://","file:///").replace("file:////", "file:///"),
       server: URLExt.join('ws://jupyter-kite', language),
       socket: URLExt.join(
         wsBase,