diff --git a/site-modules/profile/files/varnish/early_vcl_recv.vcl b/site-modules/profile/files/varnish/early_vcl_recv.vcl
index 86013883..bbda40b7 100644
--- a/site-modules/profile/files/varnish/early_vcl_recv.vcl
+++ b/site-modules/profile/files/varnish/early_vcl_recv.vcl
@@ -1,13 +1,15 @@
 # 00_early_vcl_recv.vcl
 #
 # Do early manglement of the host header to simplify its future handling
 #
 # File managed by puppet. All modifications will be lost.
 
+import std;
+
 sub vcl_recv {
   # Keep original Host header in X-Swh-Original-Host.
   set req.http.x-swh-original-host = req.http.host;
 
   # Set Host header to lower case and trim trailing port number.
-  set req.http.host = regsub(req.http.host.lower(), ":[0-9]+$", "");
+  set req.http.host = regsub(std.tolower(req.http.host), ":[0-9]+$", "");
 }