diff --git a/modules/default.nix b/modules/default.nix
index 3b1eb55..5ce52c6 100644
--- a/modules/default.nix
+++ b/modules/default.nix
@@ -57,11 +57,16 @@ in
                   default = name;
                   defaultText = lib.literalMD "Defaults to attribute name in services.tvix-binary-cache.caches";
                 };
+                remote-path-info-service-addr = lib.mkOption {
+                  type = with lib.types; nullOr str;
+                  description = "Upstream cache to substitute from if nothing in ";
+                  example = "nix+https://cache.nixos.org?trusted-public-keys=cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY=";
+                  default = null;
+                };
               };
             }
           )
         );
-
       };
     };
   };
@@ -114,6 +119,9 @@ in
               BLOB_SERVICE_ADDR = "grpc+unix://%t/tvix-castore/socket";
               DIRECTORY_SERVICE_ADDR = "grpc+unix://%t/tvix-castore/socket";
               PATH_INFO_SERVICE_ADDR = "sled://%S/${stateDir}/pathinfo.sled";
+              REMOTE_PATH_INFO_SERVICE_ADDR = lib.mkIf (
+                cfg.remote-path-info-service-addr != null
+              ) cfg.remote-path-info-service-addr;
             };
             serviceConfig = {
               ExecStart = "${pkgs.tvix-store}/bin/tvix-store --otlp=false daemon --listen-address=\"%t/${stateDir}/socket\"";