diff --git a/secure-access-token-authorizer.nix b/secure-access-token-authorizer.nix
index cb825d72a6899b9bbd278a033b9198dfdf16ac0f..65de5cd57f7a23770de625d471abd7108c76e7a3 100644
--- a/secure-access-token-authorizer.nix
+++ b/secure-access-token-authorizer.nix
@@ -22,6 +22,7 @@ buildPythonPackage rec {
   ];
 
   checkPhase = ''
+    ${pythonPackages.pyflakes}/bin/pyflakes src/_secureaccesstokenauthorizer
     ${pythonPackages.twisted}/bin/trial _secureaccesstokenauthorizer
   '';
 }