diff --git a/testing/mochitest/server.js b/testing/mochitest/server.js
index 4bb343a86f36..e274b61623a7 100644
--- a/testing/mochitest/server.js
+++ b/testing/mochitest/server.js
@@ -211,7 +211,9 @@ function createMochitestServer(serverBasePath)
       getFile: function getFile(path)
       {
         var file = serverBasePath.clone().QueryInterface(Ci.nsILocalFile);
-        file.appendRelativePath(path);
+        path.split("/").forEach(function(p) {
+          file.appendRelativePath(p);
+        });
         return file;
       },
       QueryInterface: function(aIID) { return this; }