diff --git a/lib/OpenLayers/Util.js b/lib/OpenLayers/Util.js
index dddb2963e6..f0f1af3f3e 100644
--- a/lib/OpenLayers/Util.js
+++ b/lib/OpenLayers/Util.js
@@ -660,8 +660,8 @@ OpenLayers.Util.modifyDOMElement = function(element, id, px, sz, position,
         element.id = id;
     }
     if (px) {
-        element.style.left = px.x;
-        element.style.top = px.y;
+        element.style.left = px.x + "px";
+        element.style.top = px.y + "px";
     }
     if (sz) {
         element.style.width = sz.w + "px";