diff --git a/lib/OpenLayers/Map.js b/lib/OpenLayers/Map.js
index fd2884ca4f..59bbfffd1e 100644
--- a/lib/OpenLayers/Map.js
+++ b/lib/OpenLayers/Map.js
@@ -195,7 +195,7 @@ OpenLayers.Map.prototype = {
         // if maxResolution is specified as "auto", calculate it 
         //  based on the maxExtent and the viewSize
         //
-        if (this.maxResolution == "auto") {
+        if (this.maxResolution == "auto" || this.maxResolution == null) {
             var maxExtent = this.getMaxExtent();
             var viewSize = this.getSize();
             this.maxResolution = Math.max(maxExtent.getWidth()  / viewSize.w,