diff --git a/src/renderers/dom/shared/ReactDOMComponent.js b/src/renderers/dom/shared/ReactDOMComponent.js
index dd16e9b775d8..5885c1f6d057 100644
--- a/src/renderers/dom/shared/ReactDOMComponent.js
+++ b/src/renderers/dom/shared/ReactDOMComponent.js
@@ -624,6 +624,9 @@ ReactDOMComponent.Mixin = {
         } else if (props.is) {
           el = ownerDocument.createElement(this._currentElement.type, props.is);
         } else {
+          // Separate else branch instead of using `props.is || undefined` above becuase of a Firefox bug.
+          // See discussion in https://github.com/facebook/react/pull/6896
+          // and discussion in https://bugzilla.mozilla.org/show_bug.cgi?id=1276240
           el = ownerDocument.createElement(this._currentElement.type);
         }
       } else {