diff --git a/pkgs/development/python-modules/ndjson/default.nix b/pkgs/development/python-modules/ndjson/default.nix
index 715a1989b455..b69e8401eb51 100644
--- a/pkgs/development/python-modules/ndjson/default.nix
+++ b/pkgs/development/python-modules/ndjson/default.nix
@@ -16,6 +16,7 @@ buildPythonPackage rec {
     homepage = "https://github.com/rhgrant10/ndjson";
     description = "JsonDecoder";
     platforms = platforms.unix;
+    license = licenses.gpl3Only;
     maintainers = with maintainers; [ freezeboy ];
   };
 }