diff --git a/google-map-marker.html b/google-map-marker.html
index fb789a3..32b981d 100644
--- a/google-map-marker.html
+++ b/google-map-marker.html
@@ -394,7 +394,8 @@
           this._contentObserver = new MutationObserver( this._contentChanged.bind(this));
           this._contentObserver.observe( this, {
             childList: true,
-            subtree: true
+            subtree: true,
+            characterData: true
           });
 
           var content = this.innerHTML.trim();
@@ -458,9 +459,11 @@
         },
 
         _clearListener: function(name) {
-          if (this._listeners[name]) {
-            google.maps.event.removeListener(this._listeners[name]);
-            this._listeners[name] = null;
+          if (typeof this._listeners != 'undefined'){
+              if (this._listeners[name]) {
+                google.maps.event.removeListener(this._listeners[name]);
+                this._listeners[name] = null;
+              }
           }
         },
 
diff --git a/google-map.html b/google-map.html
index 833897a..ad0d175 100644
--- a/google-map.html
+++ b/google-map.html
@@ -323,6 +323,15 @@
           value: false,
           observer: '_disableZoomChanged'
         },
+          
+        /**
+         * If true, prevent the user from zooming the map by mouse scroll wheel.
+         */
+        disableScrollWheelZoom:{
+          type: Boolean,
+          value: false,
+          observer: '_disableZoomChanged'
+        },
 
         /**
          * If set, custom styles can be applied to the map.
@@ -457,7 +466,7 @@
 
       detached: function() {
         if (this._markersChildrenListener) {
-          this.unlisten(this.$.selector, 'items-changed', '_updateMarkers');
+          this.unlisten(this.$.selector, 'iron-items-changed', '_updateMarkers');
           this._markersChildrenListener = null;
         }
         if (this._objectsMutationObserver) {
@@ -500,7 +509,7 @@
           mapTypeControl: !this.disableDefaultUi && !this.disableMapTypeControl,
           streetViewControl: !this.disableDefaultUi && !this.disableStreetViewControl,
           disableDoubleClickZoom: this.disableZoom,
-          scrollwheel: !this.disableZoom,
+          scrollwheel: !this.disableScrollWheelZoom,
           styles: this.styles,
           maxZoom: Number(this.maxZoom),
           minZoom: Number(this.minZoom)
@@ -531,7 +540,7 @@
         if (this._markersChildrenListener) {
           return;
         }
-        this._markersChildrenListener = this.listen(this.$.selector, 'items-changed', '_updateMarkers');
+        this._markersChildrenListener = this.listen(this.$.selector, 'iron-items-changed', '_updateMarkers');
       },
 
       _updateMarkers: function() {