diff --git a/pkgs/applications/version-management/monotone-viz/default.nix b/pkgs/applications/version-management/monotone-viz/default.nix
index 255192a91282..7b8b0598925e 100644
--- a/pkgs/applications/version-management/monotone-viz/default.nix
+++ b/pkgs/applications/version-management/monotone-viz/default.nix
@@ -11,7 +11,7 @@ stdenv.mkDerivation rec {
   version = "1.0.2";
   name = "monotone-viz-${version}";
 
-  buildInputs = [ocaml lablgtk libgnomecanvas glib pkgconfig graphviz_2_0 makeWrapper];
+  buildInputs = [ocaml lablgtk libgnomecanvas glib pkgconfig graphviz_2_0 makeWrapper camlp4];
   src = fetchurl {
     url = "http://oandrieu.nerim.net/monotone-viz/${name}-nolablgtk.tar.gz";
     sha256 = "1l5x4xqz5g1aaqbc1x80mg0yzkiah9ma9k9mivmn08alkjlakkdk";