diff --git a/homeassistant/components/sma/__init__.py b/homeassistant/components/sma/__init__.py
index febd4e34aaf..d8a7929ae79 100644
--- a/homeassistant/components/sma/__init__.py
+++ b/homeassistant/components/sma/__init__.py
@@ -135,3 +135,21 @@ async def async_unload_entry(hass: HomeAssistant, entry: ConfigEntry) -> bool:
         data[PYSMA_REMOVE_LISTENER]()
 
     return unload_ok
+
+
+async def async_migrate_entry(hass: HomeAssistant, entry: ConfigEntry) -> bool:
+    """Migrate entry."""
+
+    _LOGGER.debug("Migrating from version %s", entry.version)
+
+    if entry.version == 1:
+        # 1 -> 2: Unique ID from integer to string
+        if entry.minor_version == 1:
+            minor_version = 2
+            hass.config_entries.async_update_entry(
+                entry, unique_id=str(entry.unique_id), minor_version=minor_version
+            )
+
+    _LOGGER.debug("Migration successful")
+
+    return True
diff --git a/homeassistant/components/sma/config_flow.py b/homeassistant/components/sma/config_flow.py
index fe26cbee2c8..4b3e01a79a8 100644
--- a/homeassistant/components/sma/config_flow.py
+++ b/homeassistant/components/sma/config_flow.py
@@ -40,6 +40,7 @@ class SmaConfigFlow(ConfigFlow, domain=DOMAIN):
     """Handle a config flow for SMA."""
 
     VERSION = 1
+    MINOR_VERSION = 2
 
     def __init__(self) -> None:
         """Initialize."""
@@ -76,7 +77,7 @@ class SmaConfigFlow(ConfigFlow, domain=DOMAIN):
                 errors["base"] = "unknown"
 
             if not errors:
-                await self.async_set_unique_id(device_info["serial"])
+                await self.async_set_unique_id(str(device_info["serial"]))
                 self._abort_if_unique_id_configured(updates=self._data)
                 return self.async_create_entry(
                     title=self._data[CONF_HOST], data=self._data
diff --git a/tests/components/sma/__init__.py b/tests/components/sma/__init__.py
index aefb99cf1b1..80837c718a9 100644
--- a/tests/components/sma/__init__.py
+++ b/tests/components/sma/__init__.py
@@ -6,7 +6,7 @@ MOCK_DEVICE = {
     "manufacturer": "SMA",
     "name": "SMA Device Name",
     "type": "Sunny Boy 3.6",
-    "serial": "123456789",
+    "serial": 123456789,
 }
 
 MOCK_USER_INPUT = {
diff --git a/tests/components/sma/conftest.py b/tests/components/sma/conftest.py
index a54f478a31d..dd47a0f1055 100644
--- a/tests/components/sma/conftest.py
+++ b/tests/components/sma/conftest.py
@@ -22,9 +22,10 @@ def mock_config_entry() -> MockConfigEntry:
     return MockConfigEntry(
         domain=DOMAIN,
         title=MOCK_DEVICE["name"],
-        unique_id=MOCK_DEVICE["serial"],
+        unique_id=str(MOCK_DEVICE["serial"]),
         data=MOCK_USER_INPUT,
         source=config_entries.SOURCE_IMPORT,
+        minor_version=2,
     )
 
 
diff --git a/tests/components/sma/test_init.py b/tests/components/sma/test_init.py
new file mode 100644
index 00000000000..0cc82f49a41
--- /dev/null
+++ b/tests/components/sma/test_init.py
@@ -0,0 +1,27 @@
+"""Test the sma init file."""
+
+from homeassistant.components.sma.const import DOMAIN
+from homeassistant.config_entries import SOURCE_IMPORT
+from homeassistant.core import HomeAssistant
+
+from . import MOCK_DEVICE, MOCK_USER_INPUT, _patch_async_setup_entry
+
+from tests.common import MockConfigEntry
+
+
+async def test_migrate_entry_minor_version_1_2(hass: HomeAssistant) -> None:
+    """Test migrating a 1.1 config entry to 1.2."""
+    with _patch_async_setup_entry():
+        entry = MockConfigEntry(
+            domain=DOMAIN,
+            title=MOCK_DEVICE["name"],
+            unique_id=MOCK_DEVICE["serial"],  # Not converted to str
+            data=MOCK_USER_INPUT,
+            source=SOURCE_IMPORT,
+            minor_version=1,
+        )
+        entry.add_to_hass(hass)
+        assert await hass.config_entries.async_setup(entry.entry_id)
+        assert entry.version == 1
+        assert entry.minor_version == 2
+        assert entry.unique_id == str(MOCK_DEVICE["serial"])