diff --git a/public/src/forum/register.js b/public/src/forum/register.js
index fc7cf26b2a..6270f0c14c 100644
--- a/public/src/forum/register.js
+++ b/public/src/forum/register.js
@@ -61,7 +61,7 @@ define(function() {
 				showError(username_notify, 'Username too short!');
 			} else if (username.val().length > config.maximumUsernameLength) {
 				showError(username_notify, 'Username too long!');
-			} else if (!utils.isUserNameValid(username.val())) {
+			} else if (!utils.isUserNameValid(username.val()) || !utils.slugify(username.val())) {
 				showError(username_notify, 'Invalid username!');
 			} else {
 				socket.emit('user.exists', {
diff --git a/src/user.js b/src/user.js
index 1763b6c862..c40e17fa6d 100644
--- a/src/user.js
+++ b/src/user.js
@@ -31,7 +31,7 @@ var utils = require('./../public/src/utils.js'),
 				}
 			},
 			function(next) {
-				next(!utils.isUserNameValid(username) ? new Error('Invalid Username!') : null);
+				next((!utils.isUserNameValid(username) || !userslug) ? new Error('Invalid Username!') : null);
 			},
 			function(next) {
 				if (password !== undefined) {