diff --git a/pkgs/applications/version-management/darcs/darcs-2.nix b/pkgs/applications/version-management/darcs/darcs-2.nix
index b3d18522668..438f20bff9d 100644
--- a/pkgs/applications/version-management/darcs/darcs-2.nix
+++ b/pkgs/applications/version-management/darcs/darcs-2.nix
@@ -1,11 +1,12 @@
 {stdenv, fetchurl, ghc, zlib, ncurses, curl, perl}:
 
 stdenv.mkDerivation {
-  name = "darcs-2.0.2";
+  name = "darcs-2.1.0pre3";
   src = fetchurl {
-    url = http://darcs.net/darcs-2.0.2.tar.gz;
-    sha256 = "17plbfwz2rvzbvr9b90z55lj51ilnq22hhr38hffila1gsxqfk0n";
+    url = http://www.darcs.net/darcs-2.1.0pre3.tar.gz;
+    sha256 = "a4b63c16a20edef3e1dc06db29211b7272b51e6ef10e12924e6515fb71f58303";
   };
+
   buildInputs = [ghc zlib ncurses curl perl];
 
   NIX_LDFLAGS = "-lz";
diff --git a/pkgs/applications/version-management/darcs/default.nix b/pkgs/applications/version-management/darcs/default.nix
index fffc20d6295..336d37ad2c8 100644
--- a/pkgs/applications/version-management/darcs/default.nix
+++ b/pkgs/applications/version-management/darcs/default.nix
@@ -1,4 +1,10 @@
-{stdenv, fetchurl, ghc, zlib, ncurses, curl}:
+{stdenv, fetchurl, ghc, zlib, ncurses, curl, getConfig}:
+
+# you really should consider using darcs2 and updating your darcs-1 repos ..
+# many performance improvements have been made if you use the darcs-2 or hashed format
+# (darcs-2 is default now when runnig darcs 2.1.0)
+# lookup darcs convert and make sure you understand the one way conversion..
+assert getConfig ["darcs" "IreallyWantDarcsOne"] false;
 
 stdenv.mkDerivation {
   name = "darcs-1.0.9";
diff --git a/pkgs/top-level/all-packages.nix b/pkgs/top-level/all-packages.nix
index 56d77e5213e..4138d7f8ca5 100644
--- a/pkgs/top-level/all-packages.nix
+++ b/pkgs/top-level/all-packages.nix
@@ -6069,7 +6069,7 @@ let
   };
 
   darcs = import ../applications/version-management/darcs {
-    inherit fetchurl stdenv zlib ncurses curl;
+    inherit fetchurl stdenv zlib ncurses curl getConfig;
     ghc = ghc661;
   };