diff --git a/player/js/mask.js b/player/js/mask.js
index 4529f04..a7d694a 100644
--- a/player/js/mask.js
+++ b/player/js/mask.js
@@ -61,7 +61,7 @@
             expansor = createNS('filter');
             expansor.setAttribute('id',filterID);
             feMorph = createNS('feMorphology');
-            feMorph.setAttribute('operator','dilate');
+            feMorph.setAttribute('operator','erode');
             feMorph.setAttribute('in','SourceGraphic');
             feMorph.setAttribute('radius','0');
             expansor.appendChild(feMorph);