diff --git a/homeassistant/components/rainmachine/__init__.py b/homeassistant/components/rainmachine/__init__.py
index ef2713cc192..c29154a941c 100644
--- a/homeassistant/components/rainmachine/__init__.py
+++ b/homeassistant/components/rainmachine/__init__.py
@@ -219,10 +219,11 @@ async def async_setup_entry(  # noqa: C901
     """Set up RainMachine as config entry."""
     websession = aiohttp_client.async_get_clientsession(hass)
     client = Client(session=websession)
+    ip_address = entry.data[CONF_IP_ADDRESS]
 
     try:
         await client.load_local(
-            entry.data[CONF_IP_ADDRESS],
+            ip_address,
             entry.data[CONF_PASSWORD],
             port=entry.data[CONF_PORT],
             use_ssl=entry.data.get(CONF_SSL, DEFAULT_SSL),
@@ -238,6 +239,7 @@ async def async_setup_entry(  # noqa: C901
     if not entry.unique_id or is_ip_address(entry.unique_id):
         # If the config entry doesn't already have a unique ID, set one:
         entry_updates["unique_id"] = controller.mac
+
     if CONF_DEFAULT_ZONE_RUN_TIME in entry.data:
         # If a zone run time exists in the config entry's data, pop it and move it to
         # options:
@@ -252,6 +254,17 @@ async def async_setup_entry(  # noqa: C901
     if entry_updates:
         hass.config_entries.async_update_entry(entry, **entry_updates)
 
+    if entry.unique_id and controller.mac != entry.unique_id:
+        # If the mac address of the device does not match the unique_id
+        # of the config entry, it likely means the DHCP lease has expired
+        # and the device has been assigned a new IP address. We need to
+        # wait for the next discovery to find the device at its new address
+        # and update the config entry so we do not mix up devices.
+        raise ConfigEntryNotReady(
+            f"Unexpected device found at {ip_address}; expected {entry.unique_id}, "
+            f"found {controller.mac}"
+        )
+
     async def async_update(api_category: str) -> dict:
         """Update the appropriate API data based on a category."""
         data: dict = {}