diff --git a/pkgs/development/python-modules/keystoneauth1/default.nix b/pkgs/development/python-modules/keystoneauth1/default.nix
index 033f08f9587..c2c2235836f 100644
--- a/pkgs/development/python-modules/keystoneauth1/default.nix
+++ b/pkgs/development/python-modules/keystoneauth1/default.nix
@@ -22,6 +22,6 @@ buildPythonPackage rec {
 
   postPatch = ''
     sed -i 's@python@${python.interpreter}@' .testr.conf
-    substituteInPlace requirements.txt --replace "argparse"
+    substituteInPlace requirements.txt --replace "argparse" ""
   '';
 }