diff --git a/pkgs/applications/science/math/cntk/default.nix b/pkgs/applications/science/math/cntk/default.nix
index fe5c77be8b2..4bf922c4e16 100644
--- a/pkgs/applications/science/math/cntk/default.nix
+++ b/pkgs/applications/science/math/cntk/default.nix
@@ -1,8 +1,8 @@
-{ lib, stdenv, fetchgit, fetchFromGitHub, cmake
+{ config, lib, stdenv, fetchgit, fetchFromGitHub, cmake
 , openblas, opencv3, libzip, boost, protobuf, openmpi
 , onebitSGDSupport ? false
-, cudaSupport ? false, cudatoolkit, nvidia_x11
-, cudnnSupport ? false, cudnn
+, cudaSupport ? config.cudaSupport or false, cudatoolkit, nvidia_x11
+, cudnnSupport ? cudaSupport, cudnn
 }:
 
 assert cudnnSupport -> cudaSupport;
diff --git a/pkgs/top-level/all-packages.nix b/pkgs/top-level/all-packages.nix
index 4a87efeded7..5e668e98149 100644
--- a/pkgs/top-level/all-packages.nix
+++ b/pkgs/top-level/all-packages.nix
@@ -21862,12 +21862,9 @@ in
     opencv3 = opencv3WithoutCuda; # Used only for image loading.
   });
 
-  cntk = callPackage ../applications/science/math/cntk rec {
-    cudaSupport = pkgs.config.cudaSupport or false;
-    cudnnSupport = cudaSupport;
+  cntk = callPackage ../applications/science/math/cntk {
     inherit (linuxPackages) nvidia_x11;
-    # Used only for image loading.
-    opencv3 = opencv3WithoutCuda;
+    opencv3 = opencv3WithoutCuda; # Used only for image loading.
   };
 
   ecm = callPackage ../applications/science/math/ecm { };