diff --git a/src/ZGoBackend.hs b/src/ZGoBackend.hs
index ff68a61..bb1f5ea 100644
--- a/src/ZGoBackend.hs
+++ b/src/ZGoBackend.hs
@@ -727,8 +727,10 @@ routes pipe config = do
                                                              Nothing
                                                              (oaddress o')
                                                              ("Xero-" <>
-                                                              T.pack
-                                                                (show $ o_id o'))
+                                                              maybe
+                                                                ""
+                                                                (T.pack . show)
+                                                                (o_id o'))
                                                              now
                                                              True
                                                              (ocurrency o')