diff --git a/src/controllers/authentication.js b/src/controllers/authentication.js
index 8c952a0503..8aa609a32a 100644
--- a/src/controllers/authentication.js
+++ b/src/controllers/authentication.js
@@ -44,7 +44,7 @@ authenticationController.register = function (req, res) {
 				err = '[[error:invalid-email]]';
 			}
 
-			if (!err && !userData.username || userData.username.length < meta.config.minimumUsernameLength) {
+			if (!err && (!userData.username || userData.username.length < meta.config.minimumUsernameLength)) {
 				err = '[[error:username-too-short]]';
 			}