diff --git a/js/id/ui.js b/js/id/ui.js
index ddcd31649..403e92aee 100644
--- a/js/id/ui.js
+++ b/js/id/ui.js
@@ -28,7 +28,7 @@ iD.ui = function(context) {
             .attr('id', 'bar')
             .attr('class', 'fillD');
 
-        var m = content.append('div')
+        content.append('div')
             .attr('id', 'map')
             .call(map);
 
@@ -169,8 +169,8 @@ iD.ui = function(context) {
         var mapDimensions = map.dimensions();
 
         d3.select(window).on('resize.editor', function() {
-            mapDimensions = m.dimensions();
-            map.dimensions(m.dimensions());
+            mapDimensions = content.dimensions(null);
+            map.dimensions(mapDimensions);
         });
 
         function pan(d) {