diff --git a/pkgs/development/python-modules/pulsectl/default.nix b/pkgs/development/python-modules/pulsectl/default.nix
index 72c2689d3833..19fa273c0466 100644
--- a/pkgs/development/python-modules/pulsectl/default.nix
+++ b/pkgs/development/python-modules/pulsectl/default.nix
@@ -10,6 +10,7 @@ buildPythonPackage rec {
   };
 
   patches = [
+    # substitute library paths for libpulse and librt
     (substituteAll {
       src = ./library-paths.patch;
       libpulse = "${libpulseaudio.out}/lib/libpulse${stdenv.hostPlatform.extensions.sharedLibrary}";