diff --git a/pkgs/applications/version-management/monotone-viz/graphviz.patch b/pkgs/applications/version-management/monotone-viz/graphviz.patch
new file mode 100644
index 000000000000..e1f9bfc5f7f1
--- /dev/null
+++ b/pkgs/applications/version-management/monotone-viz/graphviz.patch
@@ -0,0 +1,34 @@
+# patch "agraph.ml"
+#  from [8ae6c9bb70bbf9fd80e4e62d9f162ac581619b9e]
+#    to [05aa88921481ac9bfe238daeb4374fbc9993caaa]
+#
+============================================================
+--- a/agraph.ml	8ae6c9bb70bbf9fd80e4e62d9f162ac581619b9e
++++ b/agraph.ml	05aa88921481ac9bfe238daeb4374fbc9993caaa
+@@ -50,8 +50,9 @@ let dot_format params agraph =
+       agraph.nodes in
+ 
+   !+ "digraph \"monotone-viz\"\n{\n" ;
+-  if params.lr_layout then
+-    !+ "  graph [rankdir=LR] ;\n" ;
++  if params.lr_layout
++  then  !+ "  graph [rankdir=LR] ;\n"
++  else  !+ "  graph [rankdir=BT] ;\n" ;
+   !+ "  graph [ranksep=\"0.25\"] ;\n" ;
+   !+ "  node [label=\"\"] ;\n" ;
+   
+@@ -222,11 +223,11 @@ let spawn_dot graph status done_cb =
+   let dot_prg = graph.layout_params.dot_program in
+   let cmd = 
+     if Viz_misc.debug "dot"
+-    then [ "/bin/sh" ; "-c" ; 
++    then [ "/bin/sh" ; "-c" ; 
+ 	   Printf.sprintf 
+ 	     "set -o pipefail ; \
+-              tee agraph.in.dot | %s -q -y -s%.0f | tee agraph.out.dot" dot_prg ppi ]
+-    else [ dot_prg ; "-q" ; "-y" ; Printf.sprintf "-s%.0f" ppi ] in
++              tee agraph.in.dot | %s -q -s%.0f | tee agraph.out.dot" dot_prg ppi ]
++    else [ dot_prg ; "-q" ; Printf.sprintf "-s%.0f" ppi ] in
+   let error fmt =
+     Printf.kprintf (fun s -> done_cb (`LAYOUT_ERROR s)) fmt in
+   try
diff --git a/pkgs/applications/version-management/monotone-viz/mtn-head.nix b/pkgs/applications/version-management/monotone-viz/mtn-head.nix
index 3674aa1e3dcc..9d9eb3a55bc8 100644
--- a/pkgs/applications/version-management/monotone-viz/mtn-head.nix
+++ b/pkgs/applications/version-management/monotone-viz/mtn-head.nix
@@ -13,12 +13,14 @@ rec {
   configureFlags = ["--with-lablgtk-dir=${lablgtk}/lib/ocaml/lablgtk2"];
 
   /* doConfigure should be specified separately */
-  phaseNames = ["doAutoconf" "doConfigure" "doMakeInstall"];
+  phaseNames = ["doAutoconf" "doPatch" "doConfigure" "doMakeInstall"];
 
   doAutoconf = fullDepEntry(''
     aclocal -I .
     autoconf -I .
   '') ["minInit" "addInputs" "doUnpack"];
+
+  patches = [ ./graphviz.patch ];
       
   name = "monotone-viz-mtn-head";
   meta = {