diff --git a/custom_components/diveracontrol/__init__.py b/custom_components/diveracontrol/__init__.py
index 5be5974..7e8514e 100644
--- a/custom_components/diveracontrol/__init__.py
+++ b/custom_components/diveracontrol/__init__.py
@@ -187,6 +187,26 @@ async def async_migrate_entry(hass: HomeAssistant, config_entry: ConfigEntry) ->
                 "Failed to remove old entity registry entries during migration"
             )
 
-    # v1.2.1: no migration needed
+    # v1.2.1: add new base_url parameter to config entry
+    if VERSION == 1 and MINOR_VERSION == 2 and PATCH_VERSION == 1:
+        _LOGGER.info(
+            "Migrating config entry to version %s.%s.%s",
+            VERSION,
+            MINOR_VERSION,
+            PATCH_VERSION,
+        )
+
+        if D_BASE_API_URL not in config_entry.data:
+            _LOGGER.info("Adding base_url to existing config entry")
+
+            hass.config_entries.async_update_entry(
+                config_entry,
+                data={
+                    **config_entry.data,
+                    D_BASE_API_URL: "https://api.divera247.com",
+                },
+                version=VERSION,
+                minor_version=MINOR_VERSION,
+            )
 
     return True
diff --git a/tests/test_config_flow.py b/tests/test_config_flow.py
index 8a51481..b2c5fd1 100644
--- a/tests/test_config_flow.py
+++ b/tests/test_config_flow.py
@@ -220,6 +220,7 @@ async def test_reconfigure(
     from custom_components.diveracontrol.const import (
         D_UPDATE_INTERVAL_ALARM,
         D_UPDATE_INTERVAL_DATA,
+        D_BASE_API_URL,
     )
 
     # Add the existing config entry to hass
@@ -270,10 +271,8 @@ async def test_reconfigure(
     assert updated_entry.data[D_API_KEY] == new_api_key
     assert updated_entry.data[D_UPDATE_INTERVAL_DATA] == new_interval_data
     assert updated_entry.data[D_UPDATE_INTERVAL_ALARM] == new_interval_alarm
-
-    # Properly unload the entry to clean up timers
-    await hass.config_entries.async_unload(mock_config_entry.entry_id)
-    await hass.async_block_till_done()
+    # Verify base_url is present from migration
+    assert D_BASE_API_URL in updated_entry.data
 
 
 async def test_reconfigure_entry_not_found(hass: HomeAssistant) -> None: