diff --git a/src/forward.rs b/src/forward.rs
index 3d0bfe4..9bc7816 100644
--- a/src/forward.rs
+++ b/src/forward.rs
@@ -161,7 +161,7 @@ pub async fn forward_register(
     // if the user has already generated an admin token, redirect too
     if let Some(token) = has_admintoken(&req) {
         lazy_static! {
-            static ref RE: Regex = Regex::new(r#"sncf_admin_token=(?P<token>[0-9A-Za-z]*)"#).expect("Error while parsing the sncf_admin_token regex");
+            static ref RE: Regex = Regex::new(r#"sncf_admin_token=(?P<token>[0-9A-Za-z_]*)"#).expect("Error while parsing the sncf_admin_token regex");
         }
         let admin_token = RE.captures(&token)
             .ok_or_else(|| {