diff --git a/pkgs/development/python-modules/pyopenssl/default.nix b/pkgs/development/python-modules/pyopenssl/default.nix
index 4e67fd0783d5..bc841cc2fd4e 100644
--- a/pkgs/development/python-modules/pyopenssl/default.nix
+++ b/pkgs/development/python-modules/pyopenssl/default.nix
@@ -36,7 +36,7 @@ buildPythonPackage rec {
 
   postPatch = ''
     # remove cryptography pin
-    sed "/cryptography/ s/,<[0-9]*//g" setup.py
+    sed -i "/cryptography/ s/,<[0-9]*//g" setup.py
   '';
 
   propagatedBuildInputs = [