diff --git a/src/VectorTileImageryProvider/VectorTileImageryProvider.js b/src/VectorTileImageryProvider/VectorTileImageryProvider.js
index 597a971..dbcc6d4 100644
--- a/src/VectorTileImageryProvider/VectorTileImageryProvider.js
+++ b/src/VectorTileImageryProvider/VectorTileImageryProvider.js
@@ -647,7 +647,7 @@ define([
             GEOJSONDRAWING: 4,
             COMPELTED: 5
         }
-        Cesium.defineProperties(VectorTileImageryProvider.prototype, {
+        Object.defineProperties(VectorTileImageryProvider.prototype, {
             /**
             *  
             * @memberof Cesium.VectorTileImageryProvider.prototype
@@ -1817,4 +1817,4 @@ define([
             }
         }
         return VectorTileImageryProvider;
-    })
\ No newline at end of file
+    })