diff --git a/Makefile b/Makefile
index 7be3a35..ec94d17 100644
--- a/Makefile
+++ b/Makefile
@@ -11,4 +11,7 @@ clean:
 test:
 	serve .
 
-.PHONY: clean test
+test-http:
+	serve -p 80 .
+
+.PHONY: clean test test-http
diff --git a/index.js b/index.js
index 1f2894a..7632ff1 100644
--- a/index.js
+++ b/index.js
@@ -58,7 +58,7 @@ exports.isRelative = function(url){
 exports.isCrossDomain = function(url){
   url = exports.parse(url);
   return url.hostname !== location.hostname
-    || url.port !== location.port
+    || url.port !== (location.port || 80)
     || url.protocol !== location.protocol;
 };