diff --git a/doc/src/sgml/mk_feature_tables.pl b/doc/src/sgml/mk_feature_tables.pl
index ee158cb1969..a9dfebfbb31 100644
--- a/doc/src/sgml/mk_feature_tables.pl
+++ b/doc/src/sgml/mk_feature_tables.pl
@@ -54,7 +54,9 @@ while (<$feat>)
 	{
 		print "  <entry>$feature_id</entry>\n";
 	}
-	print "  <entry>" . $feature_packages{$feature_id} . "</entry>\n";
+	print "  <entry>",
+		  defined($feature_packages{$feature_id}) ? $feature_packages{$feature_id} : "",
+		  "</entry>\n";
 	if ($subfeature_id)
 	{
 		print "  <entry>$subfeature_name</entry>\n";