diff --git a/docs/simplesamlphp-install.md b/docs/simplesamlphp-install.md
index 64c02c1e0a7f7a1289a4d126778da4697efd3def..fc16ae8ac338ccea559607de99f04a5234f586d9 100644
--- a/docs/simplesamlphp-install.md
+++ b/docs/simplesamlphp-install.md
@@ -21,7 +21,7 @@ Prerequisites
  * A web server capable of executing PHP scripts.
  * PHP version >= 7.2.0.
  * Support for the following PHP extensions:
-   * Always required: `date`, `dom`, `hash`, `libxml`, `openssl`, `pcre`, `SPL`, `zlib`, `json`, `mbstring`
+   * Always required: `date`, `dom`, `hash`, `intl`, `json`, `libxml`, `mbstring`, `openssl`, `pcre`, `SPL`, `zlib`
    * When automatically checking for latest versions, and used by some modules: `cURL`
    * When authenticating against an LDAP server: `ldap`
    * When authenticating against a RADIUS server: `radius`
diff --git a/modules/admin/lib/Controller/Config.php b/modules/admin/lib/Controller/Config.php
index 1d6ed78fcbba98efa5ac621c5517807d9c68e504..42d0b580ee9d78ed56a8c3b144ed642ed2fda9f8 100644
--- a/modules/admin/lib/Controller/Config.php
+++ b/modules/admin/lib/Controller/Config.php
@@ -238,6 +238,12 @@ class Config
                     'required' => Translate::noop('Regular expression support'),
                 ]
             ],
+            'intl_get_error_code' => [
+                'required' => 'required',
+                'descr' => [
+                    'required' => Translate::noop('PHP intl extension'),
+                ]
+            ],
             'json_decode' => [
                 'required' => 'required',
                 'descr' => [