diff --git a/pkgs/applications/virtualization/xen/4.15.nix b/pkgs/applications/virtualization/xen/4.15.nix
index c5c02f7e9181..11f5900ee84c 100644
--- a/pkgs/applications/virtualization/xen/4.15.nix
+++ b/pkgs/applications/virtualization/xen/4.15.nix
@@ -3,7 +3,7 @@
 , withInternalQemu ? true
 , withInternalTraditionalQemu ? true
 , withInternalSeabios ? true
-, withSeabios ? !withInternalSeabios, seabios ? null
+, withSeabios ? !withInternalSeabios, seabios
 , withInternalOVMF ? false # FIXME: tricky to build
 , withOVMF ? false, OVMF
 , withLibHVM ? false
@@ -179,6 +179,5 @@ callPackage (import ./generic.nix (rec {
   };
 
 })) ({
-  ocamlPackages = ocaml-ng.ocamlPackages_4_05;
-  pythonPackages = python3Packages;
+  ocamlPackages = ocaml-ng.ocamlPackages_4_14;
 } // args)
diff --git a/pkgs/applications/virtualization/xen/generic.nix b/pkgs/applications/virtualization/xen/generic.nix
index 2631c6ea44c2..8a687d45e28c 100644
--- a/pkgs/applications/virtualization/xen/generic.nix
+++ b/pkgs/applications/virtualization/xen/generic.nix
@@ -5,7 +5,7 @@ config:
 , bison, bzip2, checkpolicy, dev86, figlet, flex, gettext, glib
 , acpica-tools, libaio, libiconv, libuuid, ncurses, openssl, perl
 , xz, yajl, zlib
-, pythonPackages
+, python3Packages
 
 # Xen Optional
 , ocamlPackages
@@ -16,7 +16,7 @@ config:
 , util-linux, procps, systemd
 
 # Documentation
-# pythonPackages.markdown
+# python3Packages.markdown
 , fig2dev, ghostscript, texinfo, pandoc
 
 , binutils-unwrapped
@@ -71,16 +71,16 @@ stdenv.mkDerivation (rec {
 
     # Xen
     bison bzip2 checkpolicy dev86 figlet flex gettext glib acpica-tools libaio
-    libiconv libuuid ncurses openssl perl pythonPackages.python xz yajl zlib
+    libiconv libuuid ncurses openssl perl python3Packages.python xz yajl zlib
 
     # oxenstored
     ocamlPackages.findlib ocamlPackages.ocaml systemd
 
     # Python fixes
-    pythonPackages.wrapPython
+    python3Packages.wrapPython
 
     # Documentation
-    pythonPackages.markdown fig2dev ghostscript texinfo pandoc
+    python3Packages.markdown fig2dev ghostscript texinfo pandoc
 
     # Others
   ] ++ (concatMap (x: x.buildInputs or []) (attrValues config.xenfiles))