diff --git a/src/bugsy/bugsy.py b/src/bugsy/bugsy.py
index 8fa575f..e7c39fe 100644
--- a/src/bugsy/bugsy.py
+++ b/src/bugsy/bugsy.py
@@ -214,11 +214,9 @@ def _handle_errors(self, response):
             and "error" in result
             and result.get("error", False) is True
         ):
-            if (
-                "API key" in result["message"]
-                or "username or password" in result["message"]
-            ):
-                raise LoginException(result["message"], result.get("code"))
+            message = result.get("message")
+            if message and ("API key" in message or "username or password" in message):
+                raise LoginException(message, result.get("code"))
             else:
-                raise BugsyException(result["message"], result.get("code"))
+                raise BugsyException(message, result.get("code"))
         return result
diff --git a/tests/test_errors.py b/tests/test_errors.py
index 4d285dd..b94ec9b 100644
--- a/tests/test_errors.py
+++ b/tests/test_errors.py
@@ -95,6 +95,22 @@ def test_bugsyexception_raised_for_http_500_when_commenting_on_a_bug(bug_return)
     )
 
 
+@responses.activate
+def test_bugsyexception_raised_when_error_message_is_none():
+    # Bugzilla can return an error response whose "message" field is None.
+    responses.add(
+        responses.GET,
+        rest_url("bug", 2045159),
+        body=json.dumps({"error": True, "code": 102, "message": None}),
+        status=200,
+        content_type="application/json",
+    )
+    bugzilla = Bugsy()
+    with pytest.raises(BugsyException) as e:
+        bugzilla.get(2045159)
+    assert str(e.value) == "Message: None Code: 102"
+
+
 @responses.activate
 def test_bugsyexception_raised_for_http_500_when_adding_tags_to_bug_comments(
     bug_return, comments_return