diff --git a/webui/src/main/java/com/muwire/webui/FilesServlet.java b/webui/src/main/java/com/muwire/webui/FilesServlet.java
index 5f037fd9..eab98ad9 100644
--- a/webui/src/main/java/com/muwire/webui/FilesServlet.java
+++ b/webui/src/main/java/com/muwire/webui/FilesServlet.java
@@ -143,7 +143,7 @@ public class FilesServlet extends HttpServlet {
         }
         if (action.equals("share")) {
             String file = req.getParameter("file");
-            if (file == null) {
+            if (file == null || file.trim().length() == 0) {
                 resp.sendError(403, "Bad param");
                 return;
             }