diff --git a/pkgs/applications/science/math/cplex/default.nix b/pkgs/applications/science/math/cplex/default.nix
index fe3913648f8..dae5e1b76d3 100644
--- a/pkgs/applications/science/math/cplex/default.nix
+++ b/pkgs/applications/science/math/cplex/default.nix
@@ -1,4 +1,4 @@
-{ stdenv, makeWrapper, openjdk, gtk2, xorg, glibcLocales, releasePath }:
+{ stdenv, makeWrapper, openjdk, gtk2, xorg, glibcLocales, releasePath ? null }:
 
 # To use this package, you need to download your own cplex installer from IBM
 # and override the releasePath attribute to point to the location of the file.  
diff --git a/pkgs/top-level/all-packages.nix b/pkgs/top-level/all-packages.nix
index 73112b71d1f..a9c07edc2c8 100644
--- a/pkgs/top-level/all-packages.nix
+++ b/pkgs/top-level/all-packages.nix
@@ -1156,7 +1156,7 @@ in
 
   coprthr = callPackage ../development/libraries/coprthr { };
 
-  cplex = callPackage ../applications/science/math/cplex { releasePath = config.cplex.releasePath or null; };
+  cplex = callPackage ../applications/science/math/cplex (config.cplex or {});
 
   cpulimit = callPackage ../tools/misc/cpulimit { };