diff --git a/pkgs/applications/science/math/pynac/default.nix b/pkgs/applications/science/math/pynac/default.nix
index 1a059aeb1670..9bbb695a331b 100644
--- a/pkgs/applications/science/math/pynac/default.nix
+++ b/pkgs/applications/science/math/pynac/default.nix
@@ -41,6 +41,7 @@ stdenv.mkDerivation rec {
       of the full GiNaC, and it is *only* meant to be used as a Python library.
     '';
     homepage    = http://pynac.org;
+    license = licenses.gpl3;
     maintainers = with maintainers; [ timokau ];
     platforms   = platforms.linux;
   };