diff --git a/public/static/js/signup.js b/public/static/js/signup.js
index 4031b32..91836f6 100644
--- a/public/static/js/signup.js
+++ b/public/static/js/signup.js
@@ -14,6 +14,9 @@
             if (this.response.error) {
                 var errorText;
                 switch (this.response.error) {
+                    case 'email_not_valid':
+                        errorText = 'The given email address is not valid.'
+                        break;
                     case 'passwords_too_short':
                         errorText = 'The given password is too short. Please choose a password that is at least 6 characters long!'
                         break;
diff --git a/src/Controller/SignupController.php b/src/Controller/SignupController.php
index ea049bc..b50bfe2 100644
--- a/src/Controller/SignupController.php
+++ b/src/Controller/SignupController.php
@@ -43,6 +43,11 @@ class SignupController
             return new JsonContent($data);
         }
 
+        if (filter_var($this->request->post('email'), FILTER_VALIDATE_EMAIL) === false) {
+            $data = ['error' => 'email_not_valid'];
+            return new JsonContent($data);
+        }
+
         $select = new Select(\Container::$dbConnection, 'users');
         $select->columns(User::getFields());
         $select->where('email', '=', $this->request->post('email'));