diff --git a/nixos/modules/services/backup/borgmatic.nix b/nixos/modules/services/backup/borgmatic.nix
index 75dbf5fe1c77..632b7e6e72d9 100644
--- a/nixos/modules/services/backup/borgmatic.nix
+++ b/nixos/modules/services/backup/borgmatic.nix
@@ -25,7 +25,7 @@ let
         in
         {
           pg_dump_command =
-            if d.name == "all" then
+            if d.name == "all" && (!(d ? format) || isNull d.format) then
               "${as_user}${postgresql}/bin/pg_dumpall"
             else
               "${as_user}${postgresql}/bin/pg_dump";