diff --git a/babel/messages/checkers.py b/babel/messages/checkers.py
index 072a48a98..a65603150 100644
--- a/babel/messages/checkers.py
+++ b/babel/messages/checkers.py
@@ -57,6 +57,8 @@ def python_format(catalog: Catalog | None, message: Message) -> None:
     if msgstrs[0]:
         _validate_format(msgids[0], msgstrs[0])
     if message.pluralizable:
+        if msgstrs[0] and len(msgstrs) == 1:
+            _validate_format(msgids[1], msgstrs[0])
         for msgstr in msgstrs[1:]:
             if msgstr:
                 _validate_format(msgids[1], msgstr)
diff --git a/tests/messages/test_checkers.py b/tests/messages/test_checkers.py
index e4559f7e9..824495483 100644
--- a/tests/messages/test_checkers.py
+++ b/tests/messages/test_checkers.py
@@ -339,6 +339,7 @@ class TestPythonFormat:
         (('foo %s', 'bar'), ('foo')),
         (('foo %s', 'bar %d'), ('foo %s', 'bar %d', 'baz')),
         (('foo %s', 'bar %d'), ('foo %s', 'bar %d', 'baz %d', 'qux')),
+        (('foo', 'bar %s'), ('foo')),
     ])
     def test_python_format_invalid(self, msgid, msgstr):
         msg = Message(msgid, msgstr)
@@ -351,7 +352,6 @@ def test_python_format_invalid(self, msgid, msgstr):
         ('foo %s', ''),
         (('foo %s', 'bar %d'), ('foo %s', 'bar %d')),
         (('foo %s', 'bar %d'), ('foo %s', 'bar %d', 'baz %d')),
-        (('foo', 'bar %s'), ('foo')),
         (('foo', 'bar %s'), ('', '')),
         (('foo', 'bar %s'), ('foo', '')),
         (('foo %s', 'bar %d'), ('foo %s', '')),