diff --git a/googleapiclient/_helpers.py b/googleapiclient/_helpers.py
index c63d08448e..17d8bbc1a1 100644
--- a/googleapiclient/_helpers.py
+++ b/googleapiclient/_helpers.py
@@ -135,7 +135,7 @@ def positional_wrapper(*args, **kwargs):
         return positional_decorator
     else:
         args, _, _, defaults, _, _, _ = inspect.getfullargspec(max_positional_args)
-        return positional(len(args) - len(defaults))(max_positional_args)
+        return positional(len(args) - len(defaults or ()))(max_positional_args)
 
 
 def parse_unique_urlencoded(content):
diff --git a/tests/test__helpers.py b/tests/test__helpers.py
index 56df6f8807..8d520ca4ec 100644
--- a/tests/test__helpers.py
+++ b/tests/test__helpers.py
@@ -55,6 +55,24 @@ def function3(pos, kwonly=None):
         with self.assertRaises(TypeError):
             function3(1, 2)
 
+        # Unspecified positional with no default arguments.
+        @_helpers.positional
+        def function4(pos1, pos2):
+            return pos1 + pos2
+
+        self.assertEqual(function4(1, 2), 3)
+        with self.assertRaises(TypeError):
+            function4(1, 2, 3)
+
+        # Unspecified positional with no arguments.
+        @_helpers.positional
+        def function5():
+            return True
+
+        self.assertTrue(function5())
+        with self.assertRaises(TypeError):
+            function5(1)
+
     @mock.patch("googleapiclient._helpers.logger")
     def test_enforcement_warning(self, mock_logger):
         _helpers.positional_parameters_enforcement = _helpers.POSITIONAL_WARNING