diff --git a/lib/OpenLayers/Map.js b/lib/OpenLayers/Map.js
index a55bd55685..db66c0f0fa 100644
--- a/lib/OpenLayers/Map.js
+++ b/lib/OpenLayers/Map.js
@@ -497,7 +497,7 @@ OpenLayers.Map = OpenLayers.Class({
         OpenLayers.Element.addClass(this.div, 'olMap');
 
         // the viewPortDiv is the outermost div we modify
-        var id = this.div.id + "_OpenLayers_ViewPort";
+        var id = this.id + "_OpenLayers_ViewPort";
         this.viewPortDiv = OpenLayers.Util.createDiv(id, null, null, null,
                                                      "relative", null,
                                                      "hidden");
@@ -507,7 +507,7 @@ OpenLayers.Map = OpenLayers.Class({
         this.div.appendChild(this.viewPortDiv);
 
         // the layerContainerDiv is the one that holds all the layers
-        id = this.div.id + "_OpenLayers_Container";
+        id = this.id + "_OpenLayers_Container";
         this.layerContainerDiv = OpenLayers.Util.createDiv(id);
         this.layerContainerDiv.style.zIndex=this.Z_INDEX_BASE['Popup']-1;