diff --git a/src/Sources/Sources.js b/src/Sources/Sources.js
index 8f31d072a..5185693b7 100644
--- a/src/Sources/Sources.js
+++ b/src/Sources/Sources.js
@@ -228,6 +228,7 @@ export default class Sources extends Tool {
       {
         unenumerable: true,
         accessGetter: true,
+        prototype: false,
       }
     )
     objViewer.set(val)