diff --git a/pkgs/development/interpreters/ruby/gems.nix b/pkgs/development/interpreters/ruby/gems.nix
index 7b9122080b5..59b477b505e 100644
--- a/pkgs/development/interpreters/ruby/gems.nix
+++ b/pkgs/development/interpreters/ruby/gems.nix
@@ -21,7 +21,7 @@ self = rec {
   # import an attrset full of gems, then override badly behaved ones
   importGems = file: args:
     let
-      patches = callPackage ./patches.nix { gems = builtGems; };
+      patches = callPackage ./patches.nix { inherit ruby; gems = builtGems; };
       preBuilt = callPackage file ({ inherit buildRubyGem; self = builtGems; } // args);
       builtGems = self // (lib.mapAttrs (gem: deriv:
         if patches ? "${gem}"
@@ -60,6 +60,11 @@ self = rec {
     doCheck = false; # check depends on rspec!
   };
 
+  json = buildRubyGem {
+    name = "json-1.8.1";
+    sha256 = "0002bsycvizvkmk1jyv8px1hskk6wrjfk4f7x5byi8gxm6zzn6wn";
+  };
+
   rspec = rspec_3_0;
 
   rspec_3_0 = buildRubyGem {