diff --git a/pkgs/development/python-modules/dropbox/default.nix b/pkgs/development/python-modules/dropbox/default.nix
index 59eb019d66a4..58b2cb4310a3 100644
--- a/pkgs/development/python-modules/dropbox/default.nix
+++ b/pkgs/development/python-modules/dropbox/default.nix
@@ -49,7 +49,7 @@ buildPythonPackage rec {
 
   postPatch = ''
     substituteInPlace setup.py \
-      --replace "'pytest-runner==5.2.0'," ""
+      --replace-fail "'pytest-runner==5.2.0'," ""
   '';
 
   pythonImportsCheck = [ "dropbox" ];