diff --git a/ChangeLog b/ChangeLog
index addee19b..d1fd3ec2 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -21684,3 +21684,5 @@
 2021-05-12 Fred Gleason <fredg@paravelsystems.com>
 	* Updated the '--libdir=' value for './configure' for Ubuntu in
 	'INSTALL'.
+2021-05-12 Fred Gleason <fredg@paravelsystems.com>
+	* Added an 'Environmental Variables' entry for Ubuntu in 'INSTALL'.
diff --git a/INSTALL b/INSTALL
index e6ddeea9..54f98a7f 100644
--- a/INSTALL
+++ b/INSTALL
@@ -277,6 +277,8 @@ Required build packages: apache2 libexpat1-dev libexpat1 libid3-dev libcurl4-gnu
 
 Configure script invocation: ./configure --prefix=/usr --libdir=/usr/lib --libexecdir=/var/www/rd-bin --sysconfdir=/etc/apache2/conf-enabled --enable-rdxport-debug MUSICBRAINZ_LIBS="-ldiscid -lmusicbrainz5cc -lcoverartcc"
 
+Environmental variables: DOCBOOK_STYLESHEETS=/usr/share/xml/docbook/stylesheet/docbook-xsl-ns
+
 Apache Web Server Configuration: CGI processing must be enabled. This can
 be done by means of the following commands: