diff --git a/pkgs/development/python-modules/pyregion/default.nix b/pkgs/development/python-modules/pyregion/default.nix
index 115729b64766..30c63528514f 100644
--- a/pkgs/development/python-modules/pyregion/default.nix
+++ b/pkgs/development/python-modules/pyregion/default.nix
@@ -29,6 +29,7 @@ buildPythonPackage rec {
     pyparsing
     numpy
     astropy
+    cython
   ];
 
   # Upstream patches needed for the tests to pass