pythonthings
diff --git a/‎python/phonenumbers/phonenumberutil.py‎
Lines changed: 2 additions & 2 deletions b/‎python/phonenumbers/phonenumberutil.py‎
Lines changed: 2 additions & 2 deletions
diff --git a/‎python/tests/asyoutypetest.py‎
Lines changed: 9 additions & 0 deletions b/‎python/tests/asyoutypetest.py‎
Lines changed: 9 additions & 0 deletions
@@ -684,8 +684,8 @@ def _formatting_rule_has_first_group_only(national_prefix_formatting_rule):
     """Helper function to check if the national prefix formatting rule has the
     first group only, i.e., does not start with the national prefix.
     """
-    if national_prefix_formatting_rule is None:  # pragma no cover
-        return False
+    if national_prefix_formatting_rule is None:
+        return True
     return bool(fullmatch(_FIRST_GROUP_ONLY_PREFIX_PATTERN,
                           national_prefix_formatting_rule))
 
 
@@ -906,6 +906,15 @@ def testAYTFLongNDD_SG(self):
         self.assertEqual("777777 9876 789", formatter.input_digit('9'))
         self.assertEqual("777777 9876 7890", formatter.input_digit('0'))
 
+    def testAYTFNoNationalPrefixFormattingRule(self):
+        formatter = AsYouTypeFormatter("AO")
+        self.assertEqual("3", formatter.input_digit('3'));
+        self.assertEqual("33", formatter.input_digit('3'));
+        self.assertEqual("333", formatter.input_digit('3'));
+        self.assertEqual("333 3", formatter.input_digit('3'));
+        self.assertEqual("333 33", formatter.input_digit('3'));
+        self.assertEqual("333 333", formatter.input_digit('3'));
+
     def testAYTFShortNumberFormattingFix_AU(self):
         # For Australia, the national prefix is not optional when formatting.
         formatter = AsYouTypeFormatter("AU")