diff --git a/lib/OpenLayers/Request.js b/lib/OpenLayers/Request.js
index 6a72d2bb75..708759b327 100644
--- a/lib/OpenLayers/Request.js
+++ b/lib/OpenLayers/Request.js
@@ -126,7 +126,7 @@ OpenLayers.Request = {
         // create request, open, and set headers
         var request = new OpenLayers.Request.XMLHttpRequest();
         var url = OpenLayers.Util.urlAppend(config.url, 
-            OpenLayers.Util.getParameterString(config.params));
+            OpenLayers.Util.getParameterString(config.params || {}));
         var sameOrigin = !(url.indexOf("http") == 0);
         var urlParts = !sameOrigin && url.match(this.URL_SPLIT_REGEX);
         if (urlParts) {