diff --git a/adduser.php b/adduser.php
index 36f58b102..34ea943c7 100755
--- a/adduser.php
+++ b/adduser.php
@@ -17,11 +17,18 @@ else
 
 if (auth_usermanagement())
 {
-  if ($argv[1] && $argv[2] && $argv[3])
+  if (isset($argv[1]) && isset($argv[2]) && isset($argv[3]))
   {
-    if (adduser($argv[1],$argv[2],$argv[3],$argv[4]))
+    if (!user_exists($argv[1]))
     {
-      echo("User ".$argv[1]." added successfully\n");
+      if (adduser($argv[1],$argv[2],$argv[3],@$argv[4]))
+      {
+        echo("User ".$argv[1]." added successfully\n");
+      }
+    }
+    else
+    {
+      echo("User ".$argv[1]." already exists!\n");
     }
   }
   else
diff --git a/html/includes/authentication/mysql.inc.php b/html/includes/authentication/mysql.inc.php
index 74ae3f307..a145919de 100644
--- a/html/includes/authentication/mysql.inc.php
+++ b/html/includes/authentication/mysql.inc.php
@@ -32,7 +32,10 @@ function auth_usermanagement()
 
 function adduser($username, $password, $level, $email = "", $realname = "")
 {
-  mysql_query("INSERT INTO `users` (`username`,`password`,`level`, `email`, `realname`) VALUES ('".mres($username)."',MD5('".mres($password)."'),'".mres($level)."','".mres($email)."','".mres($realname)."')");
+  if (!user_exists($username))
+  {
+    mysql_query("INSERT INTO `users` (`username`,`password`,`level`, `email`, `realname`) VALUES ('".mres($username)."',MD5('".mres($password)."'),'".mres($level)."','".mres($email)."','".mres($realname)."')");
+  }
 
   return mysql_affected_rows();
 }