diff --git a/pkgs/development/python-modules/cffi/default.nix b/pkgs/development/python-modules/cffi/default.nix
index 496124bfa113..92899ed85e58 100644
--- a/pkgs/development/python-modules/cffi/default.nix
+++ b/pkgs/development/python-modules/cffi/default.nix
@@ -11,7 +11,9 @@ if isPyPy then null else buildPythonPackage rec {
 
   outputs = [ "out" "dev" ];
 
-  propagatedBuildInputs = [ libffi pycparser ];
+  buildInputs = [ libffi ];
+
+  propagatedBuildInputs = [ pycparser ];
 
   # On Darwin, the cffi tests want to hit libm a lot, and look for it in a global
   # impure search path. It's obnoxious how much repetition there is, and how difficult