diff --git a/pkgs/build-support/fetchmtn/default.nix b/pkgs/build-support/fetchmtn/default.nix
index 7fda2821905..80d9091e01d 100644
--- a/pkgs/build-support/fetchmtn/default.nix
+++ b/pkgs/build-support/fetchmtn/default.nix
@@ -1,25 +1,23 @@
 # You can specify some extra mirrors and a cache DB via options
-{stdenv, monotone, defaultDBMirrors ? [], cacheDB ? ""}:
+{stdenv, monotone, defaultDBMirrors ? [], cacheDB ? "./mtn-checkout.db"}:
 # dbs is a list of strings
 # each is an url for sync
 
 # selector is mtn selector, like h:org.example.branch
 # 
-{name ? "", dbs ? [], selector ? "", branch, md5 ? "", sha1 ? "", sha256 ? ""}:
+{name ? "mtn-checkout", dbs ? [], sha256
+, selector ? "h:" + branch, branch}:
 
 stdenv.mkDerivation {
-  name = if name != "" then name else "mtn-checkout";
   builder = ./builder.sh;
-  buildInputs = [monotone];
+  buildNativeInputs = [monotone];
 
-  outputHashAlgo = if sha256 == "" then (if sha1 == "" then "md5" else "sha1") else "sha256";
+  outputHashAlgo = "sha256";
   outputHashMode = "recursive";
-  outputHash = if sha256 == "" then (if sha1 == "" then md5 else sha1) else sha256;
+  outputHash = sha256;
 
   dbs = defaultDBMirrors ++ dbs;
-  cacheDB = if cacheDB != "" then cacheDB else "./mtn-checkout.db";
-  selector = if selector != "" then selector else "h:" + branch;
-  inherit branch;
+  inherit branch cacheDB name selector;
 
   impureEnvVars = [
     # We borrow these environment variables from the caller to allow
diff --git a/pkgs/top-level/all-packages.nix b/pkgs/top-level/all-packages.nix
index ed2ab36ad36..5520e98d5fe 100644
--- a/pkgs/top-level/all-packages.nix
+++ b/pkgs/top-level/all-packages.nix
@@ -266,11 +266,7 @@ let
 
   fetchgitrevision = import ../build-support/fetchgitrevision runCommand git;
 
-  fetchmtn = import ../build-support/fetchmtn {
-    inherit monotone stdenv;
-    cacheDB = getConfig ["fetchmtn" "cacheDB"] "";
-    defaultDBMirrors = getConfig ["fetchmtn" "defaultDBMirrors"] [];
-  };
+  fetchmtn = callPackage ../build-support/fetchmtn (getConfig ["fetchmtn"] {});
 
   fetchsvn = import ../build-support/fetchsvn {
     inherit stdenv subversion openssh;