diff --git a/adafruit_minimqtt/matcher.py b/adafruit_minimqtt/matcher.py
index 5d641ccb..141a4f05 100644
--- a/adafruit_minimqtt/matcher.py
+++ b/adafruit_minimqtt/matcher.py
@@ -11,6 +11,11 @@
 * Author(s): Yoch (https://github.com/yoch)
 """
 
+try:
+    from typing import Dict
+except ImportError:
+    pass
+
 
 class MQTTMatcher:
     """Intended to manage topic filters including wildcards.
@@ -27,14 +32,14 @@ class Node:
 
         __slots__ = "children", "content"
 
-        def __init__(self):
-            self.children = {}
+        def __init__(self) -> None:
+            self.children: Dict[str, MQTTMatcher.Node] = {}
             self.content = None
 
-    def __init__(self):
+    def __init__(self) -> None:
         self._root = self.Node()
 
-    def __setitem__(self, key, value):
+    def __setitem__(self, key: str, value) -> None:
         """Add a topic filter :key to the prefix tree
         and associate it to :value"""
         node = self._root
@@ -42,7 +47,7 @@ def __setitem__(self, key, value):
             node = node.children.setdefault(sym, self.Node())
         node.content = value
 
-    def __getitem__(self, key):
+    def __getitem__(self, key: str):
         """Retrieve the value associated with some topic filter :key"""
         try:
             node = self._root
@@ -54,7 +59,7 @@ def __getitem__(self, key):
         except KeyError:
             raise KeyError(key) from None
 
-    def __delitem__(self, key):
+    def __delitem__(self, key: str) -> None:
         """Delete the value associated with some topic filter :key"""
         lst = []
         try:
@@ -71,13 +76,13 @@ def __delitem__(self, key):
                     break
                 del parent.children[k]
 
-    def iter_match(self, topic):
+    def iter_match(self, topic: str):
         """Return an iterator on all values associated with filters
         that match the :topic"""
         lst = topic.split("/")
         normal = not topic.startswith("$")
 
-        def rec(node, i=0):
+        def rec(node: MQTTMatcher.Node, i: int = 0):
             if i == len(lst):
                 if node.content is not None:
                     yield node.content