diff --git a/js/common/view/RulerIconNode.ts b/js/common/view/RulerIconNode.ts
index d95359a4..ac935c04 100644
--- a/js/common/view/RulerIconNode.ts
+++ b/js/common/view/RulerIconNode.ts
@@ -26,6 +26,7 @@ class RulerIconNode extends RulerNode {
 
   /**
    * @param rulerNode
+   * @param zoomTransformProperty
    */
   constructor( rulerNode: GORulerNode, zoomTransformProperty: Property<ModelViewTransform2> ) {