diff --git a/gitweb/INSTALL b/gitweb/INSTALL
index 823053173c..4964a679b3 100644
--- a/gitweb/INSTALL
+++ b/gitweb/INSTALL
@@ -237,6 +237,12 @@ Requirements
  - Perl modules: CGI, Encode, Fcntl, File::Find, File::Basename.
  - web server
 
+The following optional Perl modules are required for extra features
+ - Digest::MD5 - for gravatar support
+ - CGI::Fast and FCGI - for running gitweb as FastCGI script
+ - HTML::TagCloud - for fancy tag cloud in project list view
+ - HTTP::Date or Time::ParseDate - to support If-Modified-Since for feeds
+
 
 Example web server configuration
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~