diff --git a/pkgs/development/python-modules/matplotlib/2.nix b/pkgs/development/python-modules/matplotlib/2.nix
index e0879050704..a6ee1a3bade 100644
--- a/pkgs/development/python-modules/matplotlib/2.nix
+++ b/pkgs/development/python-modules/matplotlib/2.nix
@@ -2,23 +2,15 @@
 , which, cycler, dateutil, nose, numpy, pyparsing, sphinx, tornado, kiwisolver
 , freetype, libpng, pkg-config, mock, pytz, pygobject3, gobject-introspection, functools32, subprocess32
 , fetchpatch
-, enableGhostscript ? false, ghostscript ? null, gtk3
+, enableGhostscript ? false, ghostscript, gtk3
 , enableGtk3 ? false, cairo
 # darwin has its own "MacOSX" backend
-, enableTk ? !stdenv.isDarwin, tcl ? null, tk ? null, tkinter ? null, libX11 ? null
+, enableTk ? !stdenv.isDarwin, tcl, tk, tkinter, libX11
 , enableQt ? false, pyqt4
 , Cocoa
 , pythonOlder
 }:
 
-assert enableGhostscript -> ghostscript != null;
-assert enableTk -> (tcl != null)
-                && (tk != null)
-                && (tkinter != null)
-                && (libX11 != null)
-                ;
-assert enableQt -> pyqt4 != null;
-
 buildPythonPackage rec {
   version = "2.2.3";
   pname = "matplotlib";
diff --git a/pkgs/development/python-modules/matplotlib/default.nix b/pkgs/development/python-modules/matplotlib/default.nix
index e6e8183e999..7364920cba2 100644
--- a/pkgs/development/python-modules/matplotlib/default.nix
+++ b/pkgs/development/python-modules/matplotlib/default.nix
@@ -2,23 +2,15 @@
 , which, cycler, dateutil, nose, numpy, pyparsing, sphinx, tornado, kiwisolver
 , freetype, qhull, libpng, pkg-config, mock, pytz, pygobject3, gobject-introspection
 , certifi, pillow
-, enableGhostscript ? true, ghostscript ? null, gtk3
+, enableGhostscript ? true, ghostscript, gtk3
 , enableGtk3 ? false, cairo
 # darwin has its own "MacOSX" backend
-, enableTk ? !stdenv.isDarwin, tcl ? null, tk ? null, tkinter ? null, libX11 ? null
-, enableQt ? false, pyqt5 ? null
+, enableTk ? !stdenv.isDarwin, tcl, tk, tkinter, libX11
+, enableQt ? false, pyqt5
 , Cocoa
 , pythonOlder
 }:
 
-assert enableGhostscript -> ghostscript != null;
-assert enableTk -> (tcl != null)
-                && (tk != null)
-                && (tkinter != null)
-                && (libX11 != null)
-                ;
-assert enableQt -> pyqt5 != null;
-
 buildPythonPackage rec {
   version = "3.4.1";
   pname = "matplotlib";