diff --git a/hooks/subjects.pl b/hooks/subjects.pl
index dee8b0e..45836b3 100755
--- a/hooks/subjects.pl
+++ b/hooks/subjects.pl
@@ -98,7 +98,7 @@ sub tag_project
 
 	$project_id .= "-" . $_[1];
     }
-    lc $project_id;
+    $project_id = lc $project_id;
     $project_id =~ s/[^a-z0-9-_]/_/g;
 
     my $year;