diff --git a/pkgs/tools/misc/sl/default.nix b/pkgs/tools/misc/sl/default.nix
index a2dab4e0eb8..aa35461a7a9 100644
--- a/pkgs/tools/misc/sl/default.nix
+++ b/pkgs/tools/misc/sl/default.nix
@@ -21,7 +21,11 @@ stdenv.mkDerivation {
 
   meta = {
     homepage = http://www.tkl.iis.u-tokyo.ac.jp/~toyoda/index_e.html;
-    license = stdenv.lib.licenses.unfree; # I couldn't find its license, only a copyright.
+    license = rec {
+      shortName = "Toyoda Masashi's free software license";
+      fullName = shortName;
+      url = https://github.com/mtoyoda/sl/blob/master/LICENSE;
+    };
     description = "Steam Locomotive runs across your terminal when you type 'sl'";
     platforms = with stdenv.lib.platforms; linux;
   };