diff --git a/pkgs/shells/rc/default.nix b/pkgs/shells/rc/default.nix
index af43c42dd4b..804919665ec 100644
--- a/pkgs/shells/rc/default.nix
+++ b/pkgs/shells/rc/default.nix
@@ -1,42 +1,44 @@
-{ lib, stdenv, fetchurl, autoreconfHook
-, ncurses #acinclude.m4 wants headers for tgetent().
-, historySupport ? false
-, readline ? null
-}:
+{ lib, stdenv, fetchFromGitHub, autoreconfHook, byacc
+, ncurses, readline
+, historySupport ? false, readlineSupport ? true }:
 
 stdenv.mkDerivation rec {
   pname = "rc";
-  version = "1.7.4";
+  version = "unstable-2021-08-03";
 
-  src = fetchurl {
-    url = "http://static.tobold.org/rc/rc-${version}.tar.gz";
-    sha256 = "1n5zz6d6z4z6s3fwa0pscqqawy561k4xfnmi91i626hcvls67ljy";
+  src = fetchFromGitHub {
+    owner = "rakitzis";
+    repo = "rc";
+    rev = "8ca9ab1305c3e30cd064290081d6e5a1fa841d26";
+    sha256 = "0744ars6y9zzsjr9xazms91qy6bi7msg2gg87526waziahfh4s4z";
   };
 
   nativeBuildInputs = [ autoreconfHook ];
-  buildInputs = [ ncurses ]
-    ++ lib.optionals (readline != null) [ readline ];
+
+  # acinclude.m4 wants headers for tgetent().
+  buildInputs = [ byacc ncurses ]
+    ++ lib.optionals readlineSupport [ readline ];
 
   configureFlags = [
     "--enable-def-interp=${stdenv.shell}" #183
     ] ++ lib.optionals historySupport [ "--with-history" ]
-    ++ lib.optionals (readline != null) [ "--with-edit=readline" ];
+    ++ lib.optionals readlineSupport [ "--with-edit=readline" ];
 
-  prePatch = ''
+  #reproducible-build
+  postPatch = ''
     substituteInPlace configure.ac \
-      --replace "date -I" "echo 2015-05-13" #reproducible-build
+      --replace "$(git describe || echo '(git description unavailable)')" "${builtins.substring 0 7 src.rev}"
   '';
 
-  passthru = {
-    shellPath = "/bin/rc";
-  };
+  passthru.shellPath = "/bin/rc";
 
   meta = with lib; {
     description = "The Plan 9 shell";
-    longDescription = "Byron Rakitzis' UNIX reimplementation of Tom Duff's Plan 9 shell.";
-    homepage = "http://tobold.org/article/rc";
+    longDescription = "Byron Rakitzis' UNIX reimplementation of Tom Duff's Plan 9 shell";
+    homepage = "https://web.archive.org/web/20180820053030/tobold.org/article/rc";
     license = with licenses; zlib;
     maintainers = with maintainers; [ ramkromberg ];
+    mainProgram = "rc";
     platforms = with platforms; all;
   };
 }