diff --git a/core/mutator.js b/core/mutator.js
index f00cd0247..8b3e46963 100644
--- a/core/mutator.js
+++ b/core/mutator.js
@@ -76,6 +76,7 @@ Blockly.Mutator.prototype.setBlock = function(block) {
  * Returns the workspace inside this mutator icon's bubble.
  * @return {Blockly.WorkspaceSvg} The workspace inside this mutator icon's
  *     bubble.
+ * @package
  */
 Blockly.Mutator.prototype.getWorkspace = function() {
   return this.workspace_;