diff --git a/pkgs/development/python-modules/generic/default.nix b/pkgs/development/python-modules/generic/default.nix
index e46c710067da..e576e3bde999 100644
--- a/pkgs/development/python-modules/generic/default.nix
+++ b/pkgs/development/python-modules/generic/default.nix
@@ -47,6 +47,7 @@ python.stdenv.mkDerivation (attrs // {
 
   name = namePrefix + name;
 
+  # checkPhase after installPhase to run tests on installed packages
   phases = "unpackPhase patchPhase configurePhase buildPhase installPhase checkPhase fixupPhase distPhase";
 
   buildInputs = [ python wrapPython setuptools ] ++ buildInputs ++ pythonPath;