diff --git a/README.md b/README.md
index 7580c84a..c5df1aa3 100644
--- a/README.md
+++ b/README.md
@@ -19,10 +19,12 @@ Also, this project is not meant to be used for commercial puposes of any kind!
 ## Requirements
 
 + Webserver running PHP ≥ 7.1 including extensions:
-  + SimpleXML
-  + GD
-  + Mysqli
-  + mbString
+  + [SimpleXML](https://www.php.net/manual/en/book.simplexml.php)
+  + [GD](https://www.php.net/manual/en/book.image)
+  + [MySQL Improved](https://www.php.net/manual/en/book.mysqli.php)
+  + [Multibyte String](https://www.php.net/manual/en/book.mbstring.php)
+  + [File Information](https://www.php.net/manual/en/book.fileinfo.php)
+  + [GNU Multiple Precision](https://www.php.net/manual/en/book.gmp.php) (When using TrinityCore as auth source)
 + MySQL ≥ 5.5.30
 + [TDB 335.20071](https://github.com/TrinityCore/TrinityCore/releases/tag/TDB335.20071) including updates up to [TrinityCore/TrinityCore@fb2ab8f](https://github.com/TrinityCore/aowow/commit/fb2ab8f61320a7afda96322cca64e0034f174309)
   + If you are using TrinityCores auth and need time to transition, use the branch *sha1-auth* in the meantime!
diff --git a/includes/ajaxHandler/admin.class.php b/includes/ajaxHandler/admin.class.php
index 3f55f7f2..5e26a1b3 100644
--- a/includes/ajaxHandler/admin.class.php
+++ b/includes/ajaxHandler/admin.class.php
@@ -526,6 +526,17 @@ class AjaxAdmin extends AjaxHandler
                     return Profiler::queueStart($msg);
                 };
                 break;
+            case 'acc_auth_mode':
+                $fn = function($x) use (&$msg) {
+                    if ($x == 1 && !extension_loaded('gmp'))
+                    {
+                        $msg .= 'PHP extension GMP is required to use TrinityCore as auth source, but is not currently enabled.<br />';
+                        return false;
+                    }
+
+                    return true;
+                };
+                break;
             default:                                        // nothing to do, everything is fine
                 return true;
         }
diff --git a/includes/shared.php b/includes/shared.php
index 62d008e3..a6586514 100644
--- a/includes/shared.php
+++ b/includes/shared.php
@@ -4,7 +4,7 @@ define('AOWOW_REVISION', 31);
 define('CLI', PHP_SAPI === 'cli');
 
 
-$reqExt = ['SimpleXML', 'gd', 'mysqli', 'mbstring', 'fileinfo'];
+$reqExt = ['SimpleXML', 'gd', 'mysqli', 'mbstring', 'fileinfo'/*, 'gmp'*/];
 $error  = '';
 foreach ($reqExt as $r)
     if (!extension_loaded($r))
diff --git a/setup/tools/clisetup/siteconfig.func.php b/setup/tools/clisetup/siteconfig.func.php
index e68c8464..193198c7 100644
--- a/setup/tools/clisetup/siteconfig.func.php
+++ b/setup/tools/clisetup/siteconfig.func.php
@@ -59,6 +59,17 @@ function siteconfig()
                     return $ok;
                 };
                 break;
+            case 'acc_auth_mode':
+                $fn = function($x) {
+                    if ($x == 1 && !extension_loaded('gmp'))
+                    {
+                        CLI::write('PHP extension GMP is required to use TrinityCore as auth source, but it is currently not enabled.', CLI::LOG_ERROR);
+                        return false;
+                    }
+
+                    return true;
+                };
+                break;
             default:                                        // nothing to do, everything is fine
                 return true;
         }