diff --git a/pkgs/development/ocaml-modules/syslog/default.nix b/pkgs/development/ocaml-modules/syslog/default.nix
index e8eabcf43b3..117277fe1b6 100644
--- a/pkgs/development/ocaml-modules/syslog/default.nix
+++ b/pkgs/development/ocaml-modules/syslog/default.nix
@@ -15,6 +15,8 @@ stdenv.mkDerivation rec {
 
   buildInputs = [ ocaml findlib ];
 
+  buildFlags = [ "all" "opt" ];
+
   createFindlibDestdir = true;
 
   meta = with stdenv.lib; {