diff --git a/src/ol/feature.js b/src/ol/feature.js
index 276efe83e8..3f69d4d8a0 100644
--- a/src/ol/feature.js
+++ b/src/ol/feature.js
@@ -46,7 +46,7 @@ ol.Feature = function(opt_geometryOrValues) {
    * @private
    * @type {ol.feature.FeatureStyleFunction|undefined}
    */
-  this.styleFunction_;
+  this.styleFunction_ = undefined;
 
   /**
    * @private
diff --git a/src/ol/layer/vectorlayer.js b/src/ol/layer/vectorlayer.js
index 5123320e1b..978e0c1a2f 100644
--- a/src/ol/layer/vectorlayer.js
+++ b/src/ol/layer/vectorlayer.js
@@ -40,10 +40,10 @@ ol.layer.Vector = function(opt_options) {
 
   /**
    * Style function for use within the library.
-   * @type {ol.feature.StyleFunction}
+   * @type {ol.feature.StyleFunction|undefined}
    * @private
    */
-  this.styleFunction_;
+  this.styleFunction_ = undefined;
 
   if (goog.isDef(options.style)) {
     this.setStyle(options.style);
@@ -80,7 +80,7 @@ ol.layer.Vector.prototype.getStyle = function() {
 
 /**
  * Get the style function.
- * @return {ol.feature.StyleFunction} Layer style function.
+ * @return {ol.feature.StyleFunction|undefined} Layer style function.
  * @todo stability experimental
  */
 ol.layer.Vector.prototype.getStyleFunction = function() {