diff --git a/hems/shm/shm.go b/hems/shm/shm.go
index 3e7cdc984..158f19e58 100644
--- a/hems/shm/shm.go
+++ b/hems/shm/shm.go
@@ -26,7 +26,7 @@ const (
 	sempController   = "Sunny Home Manager"
 	sempBaseURLEnv   = "SEMP_BASE_URL"
 	sempGateway      = "urn:schemas-simple-energy-management-protocol:device:Gateway:1"
-	sempDeviceId     = "F-%s-%.12x-00" // 6 bytes
+	sempDeviceId     = "F-%s-%.12X-00" // 6 bytes
 	sempSerialNumber = "%s-%d"
 	sempCharger      = "EVCharger"
 	basePath         = "/semp"
@@ -55,11 +55,17 @@ type Config struct {
 
 // NewFromConfig creates a new SEMP instance from configuration and starts it
 func NewFromConfig(cfg Config, site site.API, addr string, router *mux.Router) error {
-	vendorId := cfg.VendorId
+	vendorId := strings.ToUpper(cfg.VendorId)
 	if vendorId == "" {
 		vendorId = "28081973"
-	} else if len(vendorId) != 8 {
-		return fmt.Errorf("invalid vendor id: %v. Must be 8 characters HEX string", vendorId)
+	} else {
+		if _, err := hex.DecodeString(cfg.VendorId); err != nil {
+			return fmt.Errorf("vendor id: %w", err)
+		}
+
+		if len(cfg.VendorId) != 8 {
+			return fmt.Errorf("invalid vendor id: %v. Must be 8 characters HEX string", vendorId)
+		}
 	}
 
 	uid, err := uuid.NewUUID()
@@ -198,7 +204,7 @@ func (s *SEMP) gatewayDescription(w http.ResponseWriter, r *http.Request) {
 		Device: Device{
 			DeviceType:      sempGateway,
 			FriendlyName:    "evcc",
-			Manufacturer:    "github.com/evcc-io/evcc",
+			Manufacturer:    "evcc.io",
 			ModelName:       serverName,
 			PresentationURL: s.hostURI,
 			UDN:             uid,
diff --git a/tests/config-shm.spec.ts b/tests/config-shm.spec.ts
index 2ff062678..c70746ed1 100644
--- a/tests/config-shm.spec.ts
+++ b/tests/config-shm.spec.ts
@@ -71,9 +71,7 @@ test.describe("SHM", () => {
       modal.getByTestId("semp-url").click(),
     ]);
     const xml = await sempPage.content();
-    expect(xml).toContain(
-      `<DeviceId>F-${VALID_VENDOR_ID}-${VALID_DEVICE_ID.toLowerCase()}-00</DeviceId>`
-    );
+    expect(xml).toContain(`<DeviceId>F-${VALID_VENDOR_ID}-${VALID_DEVICE_ID}-00</DeviceId>`);
     await sempPage.close();
 
     // uncheck allow control