python
diff --git a/‎Lib/test/test_peg_generator/test_pegen.py
Lines changed: 27 additions & 0 deletions b/‎Lib/test/test_peg_generator/test_pegen.py
Lines changed: 27 additions & 0 deletions
@@ -540,6 +540,33 @@ def test_missing_start(self) -> None:
         with self.assertRaises(GrammarError):
             parser_class = make_parser(grammar)
 
+    def test_invalid_rule_name(self) -> None:
+        grammar = """
+        start: a b
+        _a: 'a'
+        b: 'b'
+        """
+        with self.assertRaises(GrammarError):
+            parser_class = make_parser(grammar)
+
+    def test_invalid_variable_name(self) -> None:
+        grammar = """
+        start: a b
+        a: _x='a'
+        b: 'b'
+        """
+        with self.assertRaises(GrammarError):
+            parser_class = make_parser(grammar)
+
+    def test_invalid_variable_name_in_temporal_rule(self) -> None:
+        grammar = """
+        start: a b
+        a: (_x='a' | 'b') | 'c'
+        b: 'b'
+        """
+        with self.assertRaises(GrammarError):
+            parser_class = make_parser(grammar)
+
 
 class TestGrammarVisitor:
     class Visitor(GrammarVisitor):