diff --git a/pkgs/applications/version-management/git-and-tools/default.nix b/pkgs/applications/version-management/git-and-tools/default.nix
index 1b4cc3cf70b..711f4aca336 100644
--- a/pkgs/applications/version-management/git-and-tools/default.nix
+++ b/pkgs/applications/version-management/git-and-tools/default.nix
@@ -59,34 +59,8 @@ rec {
         inherit fetchurl stdenv python git;
   };
 
-  topGit = stdenv.mkDerivation rec {
-    name = "topgit-0.8-32-g8b0f1f9";
-
-    src = fetchurl {
-      url = "http://repo.or.cz/w/topgit.git/snapshot/${name}.zip";
-      sha256 = "0v3binh7wc2di57w6rdnlww30ryszzsklfdmm61sl1ildyl1klk4";
-    };
-
-    buildInputs = [unzip];
-    configurePhase = "export prefix=$out";
-
-    postInstall = ''
-      mkdir -p "$out/share/doc/${name}"
-      cp -v README "$out/share/doc/${name}"
-
-      mkdir -p $out/etc/bash_completion.d
-      make prefix=$out \
-        install
-      mv contrib/tg-completion.bash $out/etc/bash_completion.d
-    '';
-
-    meta = {
-      description = "TopGit aims to make handling of large amount of interdependent topic branches easier";
-      maintainers = [ lib.maintainers.marcweber lib.maintainers.ludo lib.maintainers.simons ];
-      homepage = http://repo.or.cz/w/topgit.git;
-      license = "GPLv2";
-      platforms = stdenv.lib.platforms.unix;
-    };
+  topGit = lib.makeOverridable (import ./topgit) {
+    inherit stdenv fetchurl unzip;
   };
 
   tig = stdenv.mkDerivation {
diff --git a/pkgs/applications/version-management/git-and-tools/topgit/default.nix b/pkgs/applications/version-management/git-and-tools/topgit/default.nix
new file mode 100644
index 00000000000..d9aeffd4297
--- /dev/null
+++ b/pkgs/applications/version-management/git-and-tools/topgit/default.nix
@@ -0,0 +1,32 @@
+{ stdenv, fetchurl, unzip }:
+
+let
+  version = "0.8-45-gd279e29";
+  lib = stdenv.lib;
+in
+stdenv.mkDerivation {
+  name = "topgit-${version}";
+
+  src = fetchurl {
+    url = "http://repo.or.cz/w/topgit.git/snapshot/topgit-${version}.zip";
+    sha256 = "0vzrng1w2k7m4z0x9h6zbrcf33dx08ly8fnbxzz3ms2k2dbsmpl6";
+  };
+
+  buildInputs = [unzip];
+  configurePhase = "export prefix=$out";
+
+  postInstall = ''
+    install -D -m 444 README "$out/share/doc/topgit-${version}/README"
+    ensureDir "$out/etc/bash_completion.d"
+    make prefix="$out" install
+    mv "contrib/tg-completion.bash" "$out/etc/bash_completion.d/"
+  '';
+
+  meta = {
+    description = "TopGit aims to make handling of large amount of interdependent topic branches easier";
+    maintainers = [ lib.maintainers.marcweber lib.maintainers.ludo lib.maintainers.simons ];
+    homepage = http://repo.or.cz/w/topgit.git;
+    license = "GPLv2";
+    platforms = stdenv.lib.platforms.unix;
+  };
+}