diff --git a/pkgs/development/python-modules/trollius/default.nix b/pkgs/development/python-modules/trollius/default.nix
index ef367c3525d3..7b61633a7fc7 100644
--- a/pkgs/development/python-modules/trollius/default.nix
+++ b/pkgs/development/python-modules/trollius/default.nix
@@ -13,7 +13,7 @@ buildPythonPackage rec {
 
   buildInputs = [ mock ];
 
-  propagatedBuildInputs = lib.optional (isPy27 || isPyPy) [ futures ];
+  propagatedBuildInputs = lib.optionals (isPy27 || isPyPy) [ futures ];
 
   patches = [
     ./tests.patch