diff --git a/pkgs/tools/filesystems/zerofree/default.nix b/pkgs/tools/filesystems/zerofree/default.nix
index 916b8509b0d..c311ac1af23 100644
--- a/pkgs/tools/filesystems/zerofree/default.nix
+++ b/pkgs/tools/filesystems/zerofree/default.nix
@@ -20,6 +20,7 @@ stdenv.mkDerivation rec {
     homepage = https://frippery.org/uml/;
     description = "Zero free blocks from ext2, ext3 and ext4 file-systems";
     platforms = stdenv.lib.platforms.linux;
+    license = stdenv.lib.licenses.gpl2;
     maintainers = [ stdenv.lib.maintainers.theuni ];
   };
 }