diff --git a/pkgs/applications/networking/irc/weechat/scripts/weechat-matrix/default.nix b/pkgs/applications/networking/irc/weechat/scripts/weechat-matrix/default.nix
index e11981c221fa..2b572df38910 100644
--- a/pkgs/applications/networking/irc/weechat/scripts/weechat-matrix/default.nix
+++ b/pkgs/applications/networking/irc/weechat/scripts/weechat-matrix/default.nix
@@ -76,11 +76,11 @@ in buildPythonPackage {
     cp contrib/matrix_decrypt.py $out/bin/matrix_decrypt
     cp contrib/matrix_sso_helper.py $out/bin/matrix_sso_helper
     substituteInPlace $out/bin/matrix_upload \
-      --replace '/usr/bin/env -S python3' '${scriptPython}/bin/python'
+      --replace-fail '/usr/bin/env -S python3' '${scriptPython}/bin/python'
     substituteInPlace $out/bin/matrix_sso_helper \
-      --replace '/usr/bin/env -S python3' '${scriptPython}/bin/python'
+      --replace-fail '/usr/bin/env -S python3' '${scriptPython}/bin/python'
     substituteInPlace $out/bin/matrix_decrypt \
-      --replace '/usr/bin/env python3' '${scriptPython}/bin/python'
+      --replace-fail '/usr/bin/env python3' '${scriptPython}/bin/python'
 
     mkdir -p $out/${python.sitePackages}
     cp -r matrix $out/${python.sitePackages}/matrix
@@ -90,8 +90,8 @@ in buildPythonPackage {
   postFixup = ''
     addToSearchPath program_PYTHONPATH $out/${python.sitePackages}
     patchPythonScript $out/share/matrix.py
-    substituteInPlace $out/${python.sitePackages}/matrix/server.py --replace \"matrix_sso_helper\" \"$out/bin/matrix_sso_helper\"
-    substituteInPlace $out/${python.sitePackages}/matrix/uploads.py --replace \"matrix_upload\" \"$out/bin/matrix_upload\"
+    substituteInPlace $out/${python.sitePackages}/matrix/server.py --replace-fail \"matrix_sso_helper\" \"$out/bin/matrix_sso_helper\"
+    substituteInPlace $out/${python.sitePackages}/matrix/uploads.py --replace-fail \"matrix_upload\" \"$out/bin/matrix_upload\"
   '';
 
   meta = with lib; {