diff --git a/lib/mixins/mutable-data.html b/lib/mixins/mutable-data.html
index 0f7ed415ee..d5b1587b6d 100644
--- a/lib/mixins/mutable-data.html
+++ b/lib/mixins/mutable-data.html
@@ -104,8 +104,6 @@
       }
 
     }
-    /** @type {boolean} */
-    MutableData.prototype.mutableData = false;
 
     return MutableData;