diff --git a/collects/scribble/scribble-common.js b/collects/scribble/scribble-common.js
index 507f914f..636aee43 100644
--- a/collects/scribble/scribble-common.js
+++ b/collects/scribble/scribble-common.js
@@ -1,6 +1,6 @@
 // Common functionality for PLT documentation pages
 
-function GetCookie(key) {
+function GetCookie(key, def) {
   if (document.cookie.length <= 0) return null;
   var cookiestrs = document.cookie.split(/; */);
   for (var i in cookiestrs) {
@@ -9,7 +9,7 @@ function GetCookie(key) {
     if (eql >= 0 && cur.substring(0,eql) == key)
       return unescape(cur.substring(eql+1));
   }
-  return null;
+  return def;
 }
 
 function SetCookie(key, val) {
@@ -28,7 +28,7 @@ function SetPLTRoot(ver, relative) {
 
 // adding index.html works because of the above
 function GotoPLTRoot(ver, relative) {
-  var u = GetCookie("PLT_Root."+ver);
+  var u = GetCookie("PLT_Root."+ver, null);
   if (u == null) return true; // no cookie: use plain up link
   // the relative path is optional, default goes to the toplevel start page
   if (!relative) relative = "index.html";
@@ -47,7 +47,7 @@ function NormalizePath(path) {
 function DoSearchKey(event, field, ver) {
   var val = field.value;
   if (event && event.keyCode == 13 && val.indexOf("...search...") < 0) {
-    var u = GetCookie("PLT_Root."+ver);
+    var u = GetCookie("PLT_Root."+ver, null);
     if (u == null) u = "../"; // default: go up
     location = u + "search/index.html" + "?q=" + escape(val);
     return false;