diff --git a/src/tiledimage.js b/src/tiledimage.js
index bece9b66..9c2fc4ed 100644
--- a/src/tiledimage.js
+++ b/src/tiledimage.js
@@ -705,7 +705,7 @@ $.extend($.TiledImage.prototype, $.EventSource.prototype, /** @lends OpenSeadrag
         };
 
         try {
-            if ($.isArray(polygons)) {
+            if (!$.isArray(polygons)) {
                 throw new Error('Provided cropping polygon is not an array');
             }
             this._croppingPolygons = polygons.map(function(polygon){