diff --git a/src/build.js b/src/build.js
index c6d1c4a9..45f032a0 100644
--- a/src/build.js
+++ b/src/build.js
@@ -12,7 +12,7 @@ fs.writeFileSync(
         // part of fix for iframing issue
         .replace('(function initHammerheadClient () {', '(function initHammerheadClient () {' +
             'if (window["%is-hammerhead%"]) throw new TypeError("already ran"); window["%is-hammerhead%"] = true;' +
-            'window.rammerheadTop = (function() {var w = window; while (w !== w.top && w.parent["%hammerhead"]) w = w.parent; return w;})();' +
+            'window.rammerheadTop = (function() {var w = window; while (w !== w.top && w.parent["%hammerhead%"]) w = w.parent; return w;})();' +
             'window.rammerheadParent = window.rammerheadTop === window ? window : window.parent;' +
             'window.distanceRammerheadTopToTop = (function() { var i=0,w=window; while (w !== window.top) {i++;w=w.parent} return i; })();' +
             'window.rammerheadAncestorOrigins = Array.from(location.ancestorOrigins).slice(0, -window.distanceRammerheadTopToTop);\n')