diff --git a/internal/services/notification/service.go b/internal/services/notification/service.go
index 0dbeb46..30750e3 100644
--- a/internal/services/notification/service.go
+++ b/internal/services/notification/service.go
@@ -95,12 +95,25 @@ func (s *Service) initFCMClient() error {
 
 	// Prepare client options; if a service account JSON string is provided, use it.
 	var opts []option.ClientOption
+	var fbConfig *firebase.Config
 	if s.config.FCMServiceAccountKey != "" {
+		var sa struct {
+			ProjectID string `json:"project_id"`
+		}
+		if err := json.Unmarshal([]byte(s.config.FCMServiceAccountKey), &sa); err != nil {
+			return fmt.Errorf("invalid FCM_SERVICE_ACCOUNT_KEY JSON: %w", err)
+		}
+		if strings.TrimSpace(sa.ProjectID) == "" {
+			return fmt.Errorf("FCM_SERVICE_ACCOUNT_KEY is missing project_id")
+		}
+		fbConfig = &firebase.Config{
+			ProjectID: strings.TrimSpace(sa.ProjectID),
+		}
 		opts = append(opts, option.WithCredentialsJSON([]byte(s.config.FCMServiceAccountKey)))
 	}
 
 	// Initialize Firebase app
-	app, err := firebase.NewApp(ctx, nil, opts...)
+	app, err := firebase.NewApp(ctx, fbConfig, opts...)
 	if err != nil {
 		return fmt.Errorf("failed to initialize Firebase app: %w", err)
 	}