diff --git a/python-mailman.spec b/python-mailman.spec
index be7eed1..5166d38 100644
--- a/python-mailman.spec
+++ b/python-mailman.spec
@@ -109,7 +109,7 @@ done
 popd
 sed '/importlib_resources/d' -i src/mailman.egg-info/requires.txt setup.py
 %python_build
-sed 's:/sbin:/usr/bin:' src/mailman/config/mailman.cfg
+sed -i 's:/sbin:/usr/bin:' src/mailman/config/mailman.cfg
 
 %install
 %if !%{with test}