diff --git a/README.md b/README.md
index ec17aada..fa5b3e49 100644
--- a/README.md
+++ b/README.md
@@ -15,6 +15,7 @@ To report bugs use [engelsystem/issues](https://github.com/engelsystem/engelsyst
    * Required modules:
      * gettext
      * json
+     * mbstring
      * PDO
        * mysql
      * xml/libxml/SimpleXML
diff --git a/composer.json b/composer.json
index 7cf1e277..c8e9f2be 100644
--- a/composer.json
+++ b/composer.json
@@ -18,6 +18,7 @@
         "ext-gettext": "*",
         "ext-json": "*",
         "ext-libxml": "*",
+        "ext-mbstring": "*",
         "ext-PDO": "*",
         "ext-SimpleXML": "*",
         "ext-xml": "*",