diff --git a/composer.json b/composer.json
index 96c10082..d47f4830 100644
--- a/composer.json
+++ b/composer.json
@@ -61,7 +61,8 @@
         "ext-libsodium": "SSH2/SFTP can make use of some algorithms provided by the libsodium-php extension.",
         "ext-openssl": "Install the OpenSSL extension in order to speed up a wide variety of cryptographic operations.",
         "ext-mcrypt": "Install the Mcrypt extension in order to speed up a few other cryptographic operations.",
-        "ext-gmp": "Install the GMP (GNU Multiple Precision) extension in order to speed up arbitrary precision integer arithmetic operations."
+        "ext-gmp": "Install the GMP (GNU Multiple Precision) extension in order to speed up arbitrary precision integer arithmetic operations.",
+        "ext-dom": "Install the DOM extension to load XML formatted public keys."
     },
     "autoload": {
         "files": [