diff --git a/src/index.html b/src/index.html
index 7b3c1ac7..02f7e200 100644
--- a/src/index.html
+++ b/src/index.html
@@ -878,6 +878,7 @@
                   <input id="control-header-radius" class="control-header-radius" type="checkbox" tabindex="-1">
                   <label for="control-header-radius"><span class="label-icon"></span> Corner radius</label>
                 </div>
+                <p class="control-header-radius-helper form-helper small">May not be visible if Theme Radius is set to 0.</p>
               </div>
             </div>
           </div>