diff --git a/pkgs/minecraft/forge-server.nix b/pkgs/minecraft/forge-server.nix
index f94515a..a3cbb1f 100644
--- a/pkgs/minecraft/forge-server.nix
+++ b/pkgs/minecraft/forge-server.nix
@@ -35,15 +35,12 @@ let
       # defer this to the *real* package build.
       rm -r installation/libraries/net/minecraft/
 
-      # The forge installer also insists on re-creating this file.
-      rm installation/libraries/de/oceanlabs/mcp/mcp_config/*/mcp_config-*-mappings.txt
-
       cp -r installation/* $out
     '';
 
     outputHashAlgo = "sha256";
     outputHashMode = "recursive";
-    outputHash = "ZRU9ytoF1BXRQ4hx2ehPgqan6vX4l2yomzNDOOWdm0Q=";
+    outputHash = "CzzQhnN+DBgOJAa9MlNhT338VcDLy2ULMTMCecmxMQ4=";
   };
 
 in stdenv.mkDerivation rec {
@@ -55,6 +52,7 @@ in stdenv.mkDerivation rec {
     # Take the input deps and patch the Minecraft server jar into our
     # libraries to create the package.
     cp -rv ${deps}/* installation/
+    chmod -R +w installation/
     java -jar forge-${version}-installer.jar --offline --installServer installation/
   '';