diff --git a/pkgs/applications/editors/emacs/elisp-packages/melpa-packages.nix b/pkgs/applications/editors/emacs/elisp-packages/melpa-packages.nix
index 8f5f1dc45a26..3c697763a5ff 100644
--- a/pkgs/applications/editors/emacs/elisp-packages/melpa-packages.nix
+++ b/pkgs/applications/editors/emacs/elisp-packages/melpa-packages.nix
@@ -322,8 +322,8 @@ let
           dontUseCmakeBuildDir = true;
           doCheck = pkgs.stdenv.isLinux;
           packageRequires = [ self.emacs ];
-          buildInputs = [ pkgs.llvmPackages.libclang self.emacs ];
-          nativeBuildInputs = [ pkgs.cmake pkgs.llvmPackages.llvm ];
+          buildInputs = old.buildInputs ++ [ pkgs.llvmPackages.libclang self.emacs ];
+          nativeBuildInputs = old.nativeBuildInputs ++ [ pkgs.cmake pkgs.llvmPackages.llvm ];
         });
 
         # tries to write a log file to $HOME