diff --git a/nixos/modules/services/mail/postfix.nix b/nixos/modules/services/mail/postfix.nix
index bdfc53c83767..86b9223eb604 100644
--- a/nixos/modules/services/mail/postfix.nix
+++ b/nixos/modules/services/mail/postfix.nix
@@ -522,6 +522,7 @@ in
                 nullOr (oneOf [
                   bool
                   int
+                  path
                   str
                   (listOf str)
                 ])