diff --git a/composer.json b/composer.json
index f0bd60e..ff18cb8 100644
--- a/composer.json
+++ b/composer.json
@@ -23,7 +23,8 @@
     ],
     "require": {
         "php": ">=5.2.0",
-        "ext-xml": "*"
+        "ext-xml": "*",
+        "ext-xmlwriter": "*"
     },
     "recommend": {
         "ext-zip": "*",