diff --git a/lib/less/browser.js b/lib/less/browser.js
index e5a1dce2b..beeb82c06 100644
--- a/lib/less/browser.js
+++ b/lib/less/browser.js
@@ -8,7 +8,8 @@ var isFileProtocol = /^(file|chrome(-extension)?|resource|qrc|app):/.test(locati
 less.env = less.env || (location.hostname == '127.0.0.1' ||
                         location.hostname == '0.0.0.0'   ||
                         location.hostname == 'localhost' ||
-                        location.port.length > 0         ||
+                        (location.port &&
+                          location.port.length > 0)      ||
                         isFileProtocol                   ? 'development'
                                                          : 'production');