diff --git a/pkgs/os-specific/linux/nvidia-x11/default.nix b/pkgs/os-specific/linux/nvidia-x11/default.nix
index 98bbaef8770..6d3bdd90849 100644
--- a/pkgs/os-specific/linux/nvidia-x11/default.nix
+++ b/pkgs/os-specific/linux/nvidia-x11/default.nix
@@ -8,6 +8,8 @@
 
 with stdenv.lib;
 
+assert (!libsOnly) -> kernel != null;
+
 let
 
   versionNumber = "331.38";
@@ -19,7 +21,7 @@ stdenv.mkDerivation {
 
   builder = ./builder.sh;
 
-  patches = optional (versionAtLeast kernel.version "3.13") ./kernel-3.13.patch ;
+  patches = optional (kernel ? version && versionAtLeast kernel.version "3.13") ./kernel-3.13.patch ;
 
   src =
     if stdenv.system == "i686-linux" then