diff --git a/pkgs/tools/networking/ssmtp/default.nix b/pkgs/tools/networking/ssmtp/default.nix
index 031f32b5362..5f6e955f8e4 100644
--- a/pkgs/tools/networking/ssmtp/default.nix
+++ b/pkgs/tools/networking/ssmtp/default.nix
@@ -33,6 +33,7 @@ stdenv.mkDerivation {
 
   meta = with stdenv.lib; {
     platforms = platforms.linux;
+    license = licenses.gpl2;
     maintainers = with maintainers; [ basvandijk ];
   };
 }