diff --git a/flake.nix b/flake.nix
index 3b0f855eaf5d60d691d08acae679b279af7a7463..3e41a5a6f3adc22a0996360b6292a17cd48c341e 100644
--- a/flake.nix
+++ b/flake.nix
@@ -30,7 +30,12 @@
       };
     in {
       checks = hslib.checks {};
-      devShells = hslib.devShells {};
+      devShells = hslib.devShells {
+        extraBuildInputs = pkgs:
+          with pkgs; [
+            zlib
+          ];
+      };
       packages = hslib.packages {};
       apps.hlint = hslib.apps.hlint {};
 
diff --git a/gbs-downloader.cabal b/gbs-downloader.cabal
index 7230760f2c9f258429beb279a52071d71b9bbd8f..a25ed0deaa377bfa1bef77a13d92ecd8c0ab9880 100644
--- a/gbs-downloader.cabal
+++ b/gbs-downloader.cabal
@@ -74,7 +74,10 @@ library
   -- other-extensions:
 
   -- Other library packages from which modules are imported.
-  build-depends:    base ^>=4.14.3.0
+  build-depends:
+    , base                     ^>=4.14.3.0
+    , tahoe-chk
+    , tahoe-great-black-swamp
 
   -- Directories containing source files.
   hs-source-dirs:   src