diff --git a/flake.nix b/flake.nix
index 8c70ef15153e6a444c51dee6bd182192295cb18f..04920402bc7831d9d136cd1d46338fd018a3cb42 100644
--- a/flake.nix
+++ b/flake.nix
@@ -83,6 +83,7 @@
               # headers and stuff.
               export PKG_CONFIG_PATH=${pkgs.lib.makeSearchPath "lib/pkgconfig" [pkgs.zlib.dev]}
 
+              ghc-pkg check -v -v
               cabal update hackage.haskell.org
               cabal run tests
             '';