diff --git a/js/markerclusterer_marker.js b/js/markerclusterer_marker.js
index 4304bb4..f22ea6f 100644
--- a/js/markerclusterer_marker.js
+++ b/js/markerclusterer_marker.js
@@ -17,6 +17,13 @@ Drupal.gmap.addHandler('gmap', function (elem) {
 
   obj.bind('init', function () {
     // Set up the markermanager.
+    // Make sure the gridSize and maxZoom are intergers.
+    if (Drupal.settings.gmap_markermanager.gridSize){
+      Drupal.settings.gmap_markermanager.gridSize = parseInt(Drupal.settings.gmap_markermanager.gridSize);
+    }
+    if (Drupal.settings.gmap_markermanager.maxZoom){
+      Drupal.settings.gmap_markermanager.maxZoom = parseInt(Drupal.settings.gmap_markermanager.maxZoom);
+    }
 	obj.mc = new MarkerClusterer(obj.map, [], {
 	  maxZoom: parseInt(Drupal.settings.gmap_markermanager["maxZoom"]),
 	  gridSize: parseInt(Drupal.settings.gmap_markermanager["gridSize"])