diff --git a/doc/conf.py b/doc/conf.py
index 3bcbe547..aa6f7eb1 100644
--- a/doc/conf.py
+++ b/doc/conf.py
@@ -59,7 +59,6 @@
 # You can specify multiple suffix as a list of string:
 #
 # source_suffix = ['.rst', '.md']
-source_suffix = ".rst"
 
 # The encoding of source files.
 source_encoding = "utf-8"
diff --git a/noxfile.py b/noxfile.py
index 2028b4a8..a5823c2f 100644
--- a/noxfile.py
+++ b/noxfile.py
@@ -478,6 +478,7 @@ def _update_po(session):
         POT_DIR,
         "--line-width",
         str(PO_LINE_WIDTH),
+        "--no-obsolete",
         *lang_args,
         *posargs,
     )