diff --git a/libraries/src/Console/AddUserCommand.php b/libraries/src/Console/AddUserCommand.php
index 578b46fa79ddf..6135830ec5541 100644
--- a/libraries/src/Console/AddUserCommand.php
+++ b/libraries/src/Console/AddUserCommand.php
@@ -167,6 +167,9 @@ protected function doExecute(InputInterface $input, OutputInterface $output): in
                 case "JLIB_DATABASE_ERROR_VALID_MAIL":
                     $this->ioStyle->error("The email address is invalid!");
                     break;
+                case "JLIB_DATABASE_ERROR_VALID_AZ09":
+                    $this->ioStyle->error("The username is invalid!");
+                    break;
             }
 
             return 1;
diff --git a/libraries/src/Table/User.php b/libraries/src/Table/User.php
index 74796b681cb24..e95108092aba3 100644
--- a/libraries/src/Table/User.php
+++ b/libraries/src/Table/User.php
@@ -217,7 +217,7 @@ public function check()
         }
 
         if (
-            preg_match('#[<>"\'%;()&\\\\]|\\.\\./#', $this->username) || StringHelper::strlen($this->username) < 2
+            preg_match('#[\s<>"\'%;()&\\\\]|\\.\\./#', $this->username) || StringHelper::strlen($this->username) < 2
             || $filterInput->clean($this->username, 'TRIM') !== $this->username || StringHelper::strlen($this->username) > 150
         ) {
             $this->setError(Text::sprintf('JLIB_DATABASE_ERROR_VALID_AZ09', 2));