diff --git a/lark/lexer.py b/lark/lexer.py
index 36ed6bc..fc50b57 100644
--- a/lark/lexer.py
+++ b/lark/lexer.py
@@ -184,7 +184,7 @@ class LineCounter:
 
         return self.char_pos == other.char_pos and self.newline_char == other.newline_char
 
-    def feed(self, token, test_newline=True):
+    def feed(self, token: Token, test_newline=True):
         """Consume a token and calculate the new line & column.
 
         As an optional optimization, set test_newline=False if token doesn't contain a newline.
diff --git a/lark/parse_tree_builder.py b/lark/parse_tree_builder.py
index fa418a9..4342b24 100644
--- a/lark/parse_tree_builder.py
+++ b/lark/parse_tree_builder.py
@@ -1,3 +1,5 @@
+from typing import List
+
 from .exceptions import GrammarError, ConfigurationError
 from .lexer import Token
 from .tree import Tree
@@ -151,7 +153,7 @@ def _should_expand(sym):
     return not sym.is_term and sym.name.startswith('_')
 
 
-def maybe_create_child_filter(expansion, keep_all_tokens, ambiguous, _empty_indices: list):
+def maybe_create_child_filter(expansion, keep_all_tokens, ambiguous, _empty_indices: List[bool]):
     # Prepare empty_indices as: How many Nones to insert at each index?
     if _empty_indices:
         assert _empty_indices.count(False) == len(expansion)