diff --git a/INSTALL.md b/INSTALL.md
index ca5bcb4..ce65698 100644
--- a/INSTALL.md
+++ b/INSTALL.md
@@ -11,7 +11,7 @@ php-mbstring (to support other character sets), sharutils (for uudecode) and
 openssl are required. 
 php7.x-sqlite3 (php must support PDO, probably 5.1+ but all testing is on 7.x).
 phpmailer is required if email confirmation is to be used.
-compface for X-Face support
+compface and php-gd for X-Face support
 These are the names for Debian packages. Other distributions should 
 also provide these in some way.