diff --git a/controllers/auth/templates/signup.pug b/controllers/auth/templates/signup.pug
index 64adfc1..7adc148 100644
--- a/controllers/auth/templates/signup.pug
+++ b/controllers/auth/templates/signup.pug
@@ -1,11 +1,11 @@
 extends ../../../templates/base.pug
 block content
-    if registeringFailed
-        .alert There was an error.
-
     .row
         .col
         .col
+            if signupFailed !== undefined
+                .alert.alert-danger #{signupFailed}
+
             form(method="POST", action=getUrl("signupTarget"))
                 .form-group
                     input.form-control(type='text', name='username', placeholder='Username', autofocus='')
diff --git a/controllers/auth/views.js b/controllers/auth/views.js
index 006dcd4..8048ec0 100644
--- a/controllers/auth/views.js
+++ b/controllers/auth/views.js
@@ -5,6 +5,12 @@ const mail = require('mail');
 const pug = require('pug');
 const config = require('settings/config');
 
+SIGNUP_ERRORS = {
+    USERNAME_ALREADY_EXISTS: "The username you want is already used.",
+    EMAIL_ALREADY_EXISTS: "The email you want is already used.",
+    UNKOWN_ERROR: "Something weird happened, i'm sorry :'(",
+};
+
 module.exports.redirectIfNotLogged = function(redirectionPage, toDecorate) {
     return function(req, res, render) {
         if (req.session.user === undefined) {
@@ -28,6 +34,11 @@ module.exports.login = function(req, res, render) {
 }
 
 module.exports.signup = function(req, res, render) {
+    if (req.session.signupFailed !== undefined) {
+        res.locals.signupFailed = req.session.signupFailed;
+        req.session.signupFailed = undefined;
+        req.session.save();
+    }
     render('signup.pug');
 }
 
@@ -70,6 +81,21 @@ module.exports.signupTarget = function(req, res, render) {
         user.save((err) => {
 
             if (err !== undefined) {
+
+                let error = SIGNUP_ERRORS.UNKOWN_ERROR;
+                switch (err.constraint) {
+                    case 'auth_user_email_key':
+                        error = SIGNUP_ERRORS.EMAIL_ALREADY_EXISTS;
+                        break;
+                    case 'auth_user_username_key':
+                        error = SIGNUP_ERRORS.USERNAME_ALREADY_EXISTS;
+                        break;
+
+                }
+
+                req.session.signupFailed = error;
+                req.session.save();
+
                 return res.redirect(getUrl('signup'));
             }