diff --git a/massive/websocket/__init__.py b/massive/websocket/__init__.py
index 7463b4cb..da11c040 100644
--- a/massive/websocket/__init__.py
+++ b/massive/websocket/__init__.py
@@ -265,7 +265,7 @@ def _parse_subscription(s: str):
         s = s.strip()
         split = s.split(".", 1)  # Split at the first period
         if len(split) != 2:
-            logger.warning("invalid subscription:", s)
+            logger.warning("invalid subscription: %s", s)
             return [None, None]
 
         return split
diff --git a/test_websocket/test_status.py b/test_websocket/test_status.py
index d333c9c8..c2bf2666 100644
--- a/test_websocket/test_status.py
+++ b/test_websocket/test_status.py
@@ -95,3 +95,13 @@ async def test_auth_reply_status_is_logged(self):
                 "Maximum number of websocket connections exceeded."
             ],
         )
+
+    async def test_invalid_subscription_is_logged(self):
+        # a topic without a channel prefix is skipped with a warning
+        c = WebSocketClient(api_key="")
+        with self.assertLogs("WebSocketClient", level="WARNING") as logs:
+            c.subscribe("AAPL")
+        self.assertEqual(
+            logs.output, ["WARNING:WebSocketClient:invalid subscription: AAPL"]
+        )
+        self.assertEqual(c.scheduled_subs, set())