diff --git a/lark/parsers/grammar_analysis.py b/lark/parsers/grammar_analysis.py
index 4386588c..28d3cb63 100644
--- a/lark/parsers/grammar_analysis.py
+++ b/lark/parsers/grammar_analysis.py
@@ -177,13 +177,13 @@ def __init__(self, parser_conf: ParserConf, debug: bool=False, strict: bool=Fals
 
         self.FIRST, self.FOLLOW, self.NULLABLE = calculate_sets(rules)
 
-    def expand_rule(self, source_rule: NonTerminal, rules_by_origin=None) -> State:
+    def expand_rule(self, source_rule: NonTerminal, rules_by_origin=None) -> OrderedSet[RulePtr]:
         "Returns all init_ptrs accessible by rule (recursive)"
 
         if rules_by_origin is None:
             rules_by_origin = self.rules_by_origin
 
-        init_ptrs = OrderedSet()
+        init_ptrs = OrderedSet[RulePtr]()
         def _expand_rule(rule: NonTerminal) -> Iterator[NonTerminal]:
             assert not rule.is_term, rule