diff --git a/pkgs/development/tools/misc/watson-ruby/default.nix b/pkgs/development/tools/misc/watson-ruby/default.nix
index 23ec0643d77d..4d17680471d2 100644
--- a/pkgs/development/tools/misc/watson-ruby/default.nix
+++ b/pkgs/development/tools/misc/watson-ruby/default.nix
@@ -4,7 +4,7 @@ stdenv.mkDerivation rec {
   pname = "watson-ruby";
   version = (import ./gemset.nix).watson-ruby.version;
 
-  phases = [ "installPhase" ];
+  dontUnpack = true;
 
   installPhase = let
     env = bundlerEnv {