diff --git a/pkgs/development/python-modules/pyflakes/default.nix b/pkgs/development/python-modules/pyflakes/default.nix
index d8cc45119482..04bc56df12d2 100644
--- a/pkgs/development/python-modules/pyflakes/default.nix
+++ b/pkgs/development/python-modules/pyflakes/default.nix
@@ -1,4 +1,4 @@
-{ stdenv, buildPythonPackage, fetchPypi, unittest2 }:
+{ stdenv, buildPythonPackage, fetchPypi, pythonOlder, unittest2 }:
 
 buildPythonPackage rec {
   pname = "pyflakes";
@@ -11,6 +11,9 @@ buildPythonPackage rec {
 
   checkInputs = [ unittest2 ];
 
+  # some tests are output dependent, which have changed slightly
+  doCheck = pythonOlder "3.9";
+
   meta = with stdenv.lib; {
     homepage = "https://launchpad.net/pyflakes";
     description = "A simple program which checks Python source files for errors";