diff --git a/pkgs/build-support/fetchrepoproject/default.nix b/pkgs/build-support/fetchrepoproject/default.nix
index 01d7fe1d0f5..78a46d4ac9b 100644
--- a/pkgs/build-support/fetchrepoproject/default.nix
+++ b/pkgs/build-support/fetchrepoproject/default.nix
@@ -1,24 +1,34 @@
-{stdenv, git, gitRepo, gnupg ? null, cacert}:
+{ stdenv, git, gitRepo, gnupg ? null, cacert }:
 
-{name, manifest, rev ? "HEAD", sha256 ? "", repoRepoURL ? "", repoRepoRev ? "", referenceDir ? "",
-localManifests ? [] }:
+{ name, manifest, rev ? "HEAD", sha256 ? "", repoRepoURL ? "", repoRepoRev ? "", referenceDir ? ""
+, localManifests ? []
+}:
 
 assert repoRepoRev != "" -> repoRepoURL != "";
 
+with stdenv.lib;
+
+let
+  extraRepoInitFlags = [
+    (optionalString (repoRepoURL != "") "--repo-url=${repoRepoURL}")
+    (optionalString (repoRepoRev != "") "--repo-branch=${repoRepoRev}")
+    (optionalString (referenceDir != "") "--reference=${referenceDir}")
+  ];
+in
+
 stdenv.mkDerivation {
-  buildCommand = with stdenv.lib; ''
+  buildCommand = ''
     mkdir ./.repo
     mkdir ./.repo/local_manifests
-    for local_manifest in ${concatMapStringsSep " " (x: "${x}") localManifests}
+    for local_manifest in ${concatMapStringsSep " " toString localManifests}
     do
       cp $local_manifest ./.repo/local_manifests/$(stripHash $local_manifest; echo $strippedName)
     done
 
     export HOME=.repo
-    repo init --manifest-url=${manifest} --manifest-branch=${rev} --depth=1 --no-clone-bundle
-    ${optionalString (repoRepoURL != "") " --repo-url=${repoRepoURL}"}
-    ${optionalString (repoRepoRev != "") " --repo-branch=${repoRepoRev}"}
-    ${optionalString (referenceDir != "") " --reference=${referenceDir}"}
+    repo init --manifest-url=${manifest} --manifest-branch=${rev} --depth=1 --no-clone-bundle \
+        ${concatStringsSep " " extraRepoInitFlags}
+
     repo sync --jobs=$NIX_BUILD_CORES --current-branch
     rm -rf $out/.repo
   '';
@@ -29,7 +39,7 @@ stdenv.mkDerivation {
     "GIT_PROXY_COMMAND" "SOCKS_SERVER"
   ];
 
-  buildInputs = [git gitRepo cacert] ++ stdenv.lib.optional (gnupg != null) [gnupg] ;
+  buildInputs = [git gitRepo cacert] ++ optional (gnupg != null) [gnupg] ;
 
   outputHashAlgo = "sha256";
   outputHashMode = "recursive";