diff --git a/src/challenge.html b/src/challenge.html
index 6854e2e..f3d181a 100644
--- a/src/challenge.html
+++ b/src/challenge.html
@@ -43,7 +43,7 @@ function get_cookie(name) {
 	return parts.pop().split(";").shift();
 }
 function submit_proof(proof) {
-	document.cookie = "mesozoa-proof="+proof+"; domain=127.0.0.1; path=/; max-age=3600; samesite=strict";
+	document.cookie = "mesozoa-proof="+proof+"; domain="+window.location.hostname+"; path=/; max-age=3600; samesite=strict";
 	window.location.reload();
 }
 function timeout(ms) {