diff --git a/parso/python/prefix.py b/parso/python/prefix.py
index 75390ae..38b750c 100644
--- a/parso/python/prefix.py
+++ b/parso/python/prefix.py
@@ -14,7 +14,7 @@ class PrefixPart:
         self.type = typ
         self.value = value
         self.spacing = spacing
-        self.start_pos = start_pos  # type: Tuple[int, int]
+        self.start_pos: Tuple[int, int] = start_pos
 
     @property
     def end_pos(self) -> Tuple[int, int]:
diff --git a/parso/tree.py b/parso/tree.py
index a54d875..312c80b 100644
--- a/parso/tree.py
+++ b/parso/tree.py
@@ -192,7 +192,7 @@ class Leaf(NodeOrLeaf):
         :py:func:`str` Typically a mixture of whitespace and comments. Stuff
         that is syntactically irrelevant for the syntax tree.
         '''
-        self.parent = None  # type: Optional[BaseNode]
+        self.parent: Optional[BaseNode] = None
         '''
         The parent :class:`BaseNode` of this leaf.
         '''
@@ -264,7 +264,7 @@ class BaseNode(NodeOrLeaf):
         """
         A list of :class:`NodeOrLeaf` child nodes.
         """
-        self.parent = None  # type: Optional[BaseNode]
+        self.parent: Optional[BaseNode] = None
         '''
         The parent :class:`BaseNode` of this leaf.
         None if this is the root node.