diff --git a/modules/clan/phonebox/default.nix b/modules/clan/phonebox/default.nix
index d9f252f..f65bdb6 100644
--- a/modules/clan/phonebox/default.nix
+++ b/modules/clan/phonebox/default.nix
@@ -299,6 +299,8 @@
                       disallow=all
                       allow=ulaw,alaw,g722,gsm
                       direct_media=no
+                      t38_udptl=yes
+                      t38_udptl_ec=redundancy
 
                       [internal_endpoint](!,base_endpoint)
                       context=from-internal