diff --git a/api/library/python/iterm2/iterm2/session.py b/api/library/python/iterm2/iterm2/session.py
index b95d5e0688..92604aa69e 100644
--- a/api/library/python/iterm2/iterm2/session.py
+++ b/api/library/python/iterm2/iterm2/session.py
@@ -175,7 +175,7 @@ class Session:
     Represents an iTerm2 session.
     """
 
-    class Delegate:
+    class Delegate(abc.ABC):
         """
         Provides callbacks for Session.
         """
@@ -183,16 +183,19 @@ class Delegate:
         def session_delegate_get_tab(
                 self, session) -> typing.Optional['iterm2.Tab']:
             """Returns the tab for a session."""
+            ...
 
         @abc.abstractmethod
         def session_delegate_get_window(
                 self, session) -> typing.Optional['iterm2.Window']:
             """Returns the window for a session."""
+            ...
 
         @abc.abstractmethod
         async def session_delegate_create_session(
                 self, session_id: str) -> typing.Optional['iterm2.session.Session']:
             """Creates a new Session object given a session ID."""
+            ...
 
     delegate: typing.Optional[Delegate] = None
 
diff --git a/api/library/python/iterm2/iterm2/tab.py b/api/library/python/iterm2/iterm2/tab.py
index 5925f5a4a5..54d58c9423 100644
--- a/api/library/python/iterm2/iterm2/tab.py
+++ b/api/library/python/iterm2/iterm2/tab.py
@@ -25,18 +25,20 @@ class Tab:
     Don't create this yourself. Instead, use :class:`~iterm2.App`."""
 
     # pylint: disable=too-few-public-methods
-    class Delegate:
+    class Delegate(abc.ABC):
         """Delegate for Tab."""
         @abc.abstractmethod
         def tab_delegate_get_window(
                 self, tab: 'Tab') -> typing.Optional['iterm2.window.Window']:
             """Returns the Window for a Tab."""
+            ...
 
         @abc.abstractmethod
         async def tab_delegate_get_window_by_id(
                 self,
                 window_id: str) -> typing.Optional['iterm2.window.Window']:
             """Returns the Window with the given ID."""
+            ...
     # pylint: enable=too-few-public-methods
 
     delegate: typing.Optional[Delegate] = None
diff --git a/api/library/python/iterm2/iterm2/tmux.py b/api/library/python/iterm2/iterm2/tmux.py
index 9273f44168..da77ef8610 100644
--- a/api/library/python/iterm2/iterm2/tmux.py
+++ b/api/library/python/iterm2/iterm2/tmux.py
@@ -11,19 +11,24 @@
 import iterm2.window
 
 
-@abc.abstractmethod
-class Delegate:
+class Delegate(abc.ABC):
     """Delegate interface for tmux."""
+    @abc.abstractmethod
     async def tmux_delegate_async_get_window_for_tab_id(
             self, tab_id: str) -> typing.Optional[iterm2.window.Window]:
         """Refreshes and gets the window for the specified tab."""
+        ...
 
+    @abc.abstractmethod
     def tmux_delegate_get_session_by_id(
             self, session_id: str) -> typing.Optional[iterm2.session.Session]:
         """Returns the session with the given ID."""
+        ...
 
+    @abc.abstractmethod
     def tmux_delegate_get_connection(self) -> iterm2.connection.Connection:
         """Returns the connection."""
+        ...
 
 
 DELEGATE: typing.Optional[Delegate] = None
diff --git a/api/library/python/iterm2/iterm2/window.py b/api/library/python/iterm2/iterm2/window.py
index 00e427d0de..a9064220ec 100644
--- a/api/library/python/iterm2/iterm2/window.py
+++ b/api/library/python/iterm2/iterm2/window.py
@@ -46,25 +46,28 @@ class Window:
     :meth:`async_create`.
     """
 
-    class Delegate:
+    class Delegate(abc.ABC):
         """Delegate for Window"""
         @abc.abstractmethod
         async def window_delegate_get_window_with_session_id(
                 self,
                 session_id: str) -> typing.Optional['Window']:
             """Gets the Window that contains a Session by ID."""
+            ...
 
         @abc.abstractmethod
         async def window_delegate_get_tab_by_id(
                 self,
                 tab_id: str) -> typing.Optional[iterm2.tab.Tab]:
             """Gets a Tab by ID."""
+            ...
 
         @abc.abstractmethod
         async def window_delegate_get_tab_with_session_id(
                 self,
                 session_id: str) -> typing.Optional[iterm2.tab.Tab]:
             """Returns the Tab containing a Session by ID."""
+            ...
 
     delegate: typing.Optional[Delegate] = None