diff --git a/pkgs/tools/text/zimwriterfs/default.nix b/pkgs/tools/text/zimwriterfs/default.nix
index 085331ce0d5..a5eeb423ff2 100644
--- a/pkgs/tools/text/zimwriterfs/default.nix
+++ b/pkgs/tools/text/zimwriterfs/default.nix
@@ -37,6 +37,7 @@ stdenv.mkDerivation rec {
     description = "A console tool to create ZIM files";
     homepage = http://git.wikimedia.org/log/openzim;
     maintainers = with stdenv.lib.maintainers; [ robbinch ];
+    license = stdenv.lib.licenses.gpl3;
     platforms = with stdenv.lib.platforms; linux;
   };
 }