diff --git a/pkgs/development/ocaml-modules/extlib/default.nix b/pkgs/development/ocaml-modules/extlib/default.nix
index 408082226221..55e1c8418305 100644
--- a/pkgs/development/ocaml-modules/extlib/default.nix
+++ b/pkgs/development/ocaml-modules/extlib/default.nix
@@ -12,7 +12,10 @@ stdenv.mkDerivation {
 
   createFindlibDestdir = true;
 
-  configurePhase = "true";
+  buildPhase = ''
+    make all
+    make opt
+  '';
 
   meta = {
     homepage = "http://code.google.com/p/ocaml-extlib/";