diff --git a/src/github3/events.py b/src/github3/events.py
index d97d2faa..f3d02272 100644
--- a/src/github3/events.py
+++ b/src/github3/events.py
@@ -392,7 +392,7 @@ class Event(models.GitHubCore):
     .. attribute:: actor
 
         A :class:`~github3.events.EventUser` that represents the user whose
-        action generated this event.
+        action generated this event, or `None` if the user no longer exists.
 
     .. attribute:: created_at
 
@@ -442,7 +442,9 @@ def _update_attributes(self, event):
         # If we don't copy this, then we end up altering _json_data which we do
         # not want to do:
         event = copy.deepcopy(event)
-        self.actor = EventUser(event["actor"], self)
+        self.actor = event["actor"]
+        if self.actor:
+            self.actor = EventUser(self.actor, self)
         self.created_at = self._strptime(event["created_at"])
         self.id = event["id"]
         self.org = event.get("org")
diff --git a/src/github3/issues/event.py b/src/github3/issues/event.py
index 356afb94..7fb5048c 100644
--- a/src/github3/issues/event.py
+++ b/src/github3/issues/event.py
@@ -60,7 +60,9 @@ class IssueEvent(GitHubCore):
 
     def _update_attributes(self, event):
         self._api = event["url"]
-        self.actor = users.ShortUser(event["actor"], self)
+        self.actor = event["actor"]
+        if self.actor:
+            self.actor = users.ShortUser(self.actor, self)
         self.commit_id = event["commit_id"]
         self.commit_url = event["commit_url"]
         self.created_at = self._strptime(event["created_at"])
diff --git a/src/github3/pulls.py b/src/github3/pulls.py
index 8c6f91d5..337f6c91 100644
--- a/src/github3/pulls.py
+++ b/src/github3/pulls.py
@@ -71,7 +71,9 @@ def _update_attributes(self, dest):
         repo = dest.get("repo")
         if repo:
             self._repo_name = repo.get("name")
-            self._repo_owner = repo["owner"]["login"]
+            self._repo_owner = repo.get("owner")
+            if self._repo_owner:
+                self._repo_owner = self._repo_owner["login"]
             self.repository = ShortRepository(repo, self)
         self.repo = (self._repo_owner, self._repo_name)
 
@@ -992,7 +994,9 @@ def _update_attributes(self, review):
         # PullReview.
         self.commit_id = review.get("commit_id", None)
         self.html_url = review["html_url"]
-        self.user = users.ShortUser(review["user"], self)
+        self.user = review["user"]
+        if self.user:
+            self.user = users.ShortUser(self.user, self)
         self.state = review["state"]
         self.submitted_at = self._strptime(review.get("submitted_at"))
         self.pull_request_url = review["pull_request_url"]
diff --git a/src/github3/repos/repo.py b/src/github3/repos/repo.py
index 12fa01cb..0d8baf7c 100644
--- a/src/github3/repos/repo.py
+++ b/src/github3/repos/repo.py
@@ -91,7 +91,9 @@ def _update_attributes(self, repo):
         self.milestones_urlt = urit.URITemplate(repo["milestones_url"])
         self.name = repo["name"]
         self.notifications_urlt = urit.URITemplate(repo["notifications_url"])
-        self.owner = users.ShortUser(repo["owner"], self)
+        self.owner = repo["owner"]
+        if self.owner:
+            self.owner = users.ShortUser(self.owner, self)
         self.private = repo["private"]
         self.pulls_urlt = urit.URITemplate(repo["pulls_url"])
         self.releases_urlt = urit.URITemplate(repo["releases_url"])