diff --git a/nix/build-support/stacklock2nix/default.nix b/nix/build-support/stacklock2nix/default.nix
index ca981d2..2431348 100644
--- a/nix/build-support/stacklock2nix/default.nix
+++ b/nix/build-support/stacklock2nix/default.nix
@@ -520,6 +520,8 @@ let
           mkdir -p "$out"
           cd "$out"
           ${lib.concatMapStrings copyForPkg pkgs}
+          # the derivation must not fail in case the very last `copyForPkg` fails
+          true
         '';
 
   # Similar to callHackage, but instead of internally running cabal2nix, it