diff --git a/tests/components/mqtt/test_common.py b/tests/components/mqtt/test_common.py
index 95a26daf562..fbf393dc105 100644
--- a/tests/components/mqtt/test_common.py
+++ b/tests/components/mqtt/test_common.py
@@ -68,7 +68,7 @@ DEFAULT_CONFIG_DEVICE_INFO_MAC = {
 
 _SENTINEL = object()
 
-DISCOVERY_COUNT = len(MQTT)
+DISCOVERY_COUNT = sum(len(discovery_topic) for discovery_topic in MQTT.values())
 DEVICE_DISCOVERY_COUNT = 2
 
 type _MqttMessageType = list[tuple[str, str]]