diff --git a/pkgs/development/tools/poetry2nix/poetry2nix/lib.nix b/pkgs/development/tools/poetry2nix/poetry2nix/lib.nix
index 39233929abb..4d3d36fd769 100644
--- a/pkgs/development/tools/poetry2nix/poetry2nix/lib.nix
+++ b/pkgs/development/tools/poetry2nix/poetry2nix/lib.nix
@@ -146,7 +146,7 @@ let
     else
       pkgs.fetchurl {
         url = predictURLFromPypi { inherit pname file hash kind; };
-        inherit hash;
+        sha256 = builtins.elemAt (builtins.match "sha256:(.*)" hash) 0; # nix 2.0 backwards compatibility.
       }
   );
   getBuildSystemPkgs =