diff --git a/test/unit/configure.html b/test/unit/configure.html
index 8fc15928ce..1158201a13 100644
--- a/test/unit/configure.html
+++ b/test/unit/configure.html
@@ -511,6 +511,10 @@
       var el = document.createElement('x-config-lazy-host');
       document.body.appendChild(el);
       Polymer(window.XConfigLazy);
+      // The purpose of this test is to test lazy upgrading an element that
+      // has a property pre-bound to it (that has an accessor) but that has
+      // no defaults for it (stresses a prior bug in ready() code that called
+      // _attachDom twice, which throws in Safari's native SD
       Polymer(window.XConfigLazyNoDefaults);
       assert.equal(el.$.lazy.noEffectProp, 1);
       assert.equal(el.$.lazy.defaultUsesNoEffectProp, 2);