diff --git a/ubuntutools/lp/lpapicache.py b/ubuntutools/lp/lpapicache.py
index 50d1a94..ac1d6c3 100644
--- a/ubuntutools/lp/lpapicache.py
+++ b/ubuntutools/lp/lpapicache.py
@@ -137,7 +137,7 @@ class BaseWrapper(object, metaclass=MetaWrapper):
     A base class from which other wrapper classes are derived.
     """
 
-    resource_type = None  # it's a base class after all
+    resource_type: str = None  # it's a base class after all
 
     def __new__(cls, data):
         if isinstance(data, str) and data.startswith(str(Launchpad._root_uri)):
diff --git a/ubuntutools/misc.py b/ubuntutools/misc.py
index 7dc7ac0..ac82f65 100644
--- a/ubuntutools/misc.py
+++ b/ubuntutools/misc.py
@@ -52,7 +52,7 @@ UPLOAD_QUEUE_STATUSES = ("New", "Unapproved", "Accepted", "Done", "Rejected")
 
 DOWNLOAD_BLOCKSIZE_DEFAULT = 8192
 
-_SYSTEM_DISTRIBUTION_CHAIN = []
+_SYSTEM_DISTRIBUTION_CHAIN: list[str] = []
 
 
 class DownloadError(Exception):