diff --git a/bffhd/authentication/fabfire_bin/server.rs b/bffhd/authentication/fabfire_bin/server.rs
index 4000513..e183f2b 100644
--- a/bffhd/authentication/fabfire_bin/server.rs
+++ b/bffhd/authentication/fabfire_bin/server.rs
@@ -142,7 +142,7 @@ impl FabFire {
             key_info: None,
             auth_info: None,
             app_id: 0x464142,
-            local_urn: "urn:fabaccess:lab:{space}".into(),
+            local_urn: format!("urn:fabaccess:lab:{space}"),
             desfire: Desfire {
                 card: None,
                 session_key: None,