diff --git a/server/server.go b/server/server.go
index 39bef7d..d8c7f15 100644
--- a/server/server.go
+++ b/server/server.go
@@ -142,11 +142,8 @@ func New(conf *Config) (*Server, error) {
 	}
 	var firebaseSubscriber subscriber
 	if conf.FirebaseKeyFile != "" {
-		sender, err := createFirebaseSender(conf)
-		if err != nil {
-			return nil, err
-		}
-		firebaseSubscriber, err = createFirebaseSubscriber(auther, sender)
+		var err error
+		firebaseSubscriber, err = createFirebaseSubscriber(conf.FirebaseKeyFile, auther)
 		if err != nil {
 			return nil, err
 		}
diff --git a/server/server_firebase.go b/server/server_firebase.go
index dea8c1c..c0e8813 100644
--- a/server/server_firebase.go
+++ b/server/server_firebase.go
@@ -10,10 +10,8 @@ import (
 	"strings"
 )
 
-type firebaseSender func(m *messaging.Message) error
-
-func createFirebaseSender(conf *Config) (firebaseSender, error) {
-	fb, err := firebase.NewApp(context.Background(), nil, option.WithCredentialsFile(conf.FirebaseKeyFile))
+func createFirebaseSubscriber(credentialsFile string, auther auth.Auther) (subscriber, error) {
+	fb, err := firebase.NewApp(context.Background(), nil, option.WithCredentialsFile(credentialsFile))
 	if err != nil {
 		return nil, err
 	}
@@ -21,69 +19,71 @@ func createFirebaseSender(conf *Config) (firebaseSender, error) {
 	if err != nil {
 		return nil, err
 	}
-	return func(m *messaging.Message) error {
-		_, err := msg.Send(context.Background(), m)
+	return func(m *message) error {
+		fbm, err := toFirebaseMessage(m, auther)
+		if err != nil {
+			return err
+		}
+		_, err = msg.Send(context.Background(), fbm)
 		return err
 	}, nil
 }
 
-func createFirebaseSubscriber(auther auth.Auther, sender firebaseSender) (subscriber, error) {
-	return func(m *message) error {
-		var data map[string]string // Mostly matches https://ntfy.sh/docs/subscribe/api/#json-message-format
-		switch m.Event {
-		case keepaliveEvent, openEvent:
+func toFirebaseMessage(m *message, auther auth.Auther) (*messaging.Message, error) {
+	var data map[string]string // Mostly matches https://ntfy.sh/docs/subscribe/api/#json-message-format
+	switch m.Event {
+	case keepaliveEvent, openEvent:
+		data = map[string]string{
+			"id":    m.ID,
+			"time":  fmt.Sprintf("%d", m.Time),
+			"event": m.Event,
+			"topic": m.Topic,
+		}
+	case messageEvent:
+		allowForward := true
+		if auther != nil {
+			allowForward = auther.Authorize(nil, m.Topic, auth.PermissionRead) == nil
+		}
+		if allowForward {
+			data = map[string]string{
+				"id":       m.ID,
+				"time":     fmt.Sprintf("%d", m.Time),
+				"event":    m.Event,
+				"topic":    m.Topic,
+				"priority": fmt.Sprintf("%d", m.Priority),
+				"tags":     strings.Join(m.Tags, ","),
+				"click":    m.Click,
+				"title":    m.Title,
+				"message":  m.Message,
+				"encoding": m.Encoding,
+			}
+			if m.Attachment != nil {
+				data["attachment_name"] = m.Attachment.Name
+				data["attachment_type"] = m.Attachment.Type
+				data["attachment_size"] = fmt.Sprintf("%d", m.Attachment.Size)
+				data["attachment_expires"] = fmt.Sprintf("%d", m.Attachment.Expires)
+				data["attachment_url"] = m.Attachment.URL
+			}
+		} else {
+			// If anonymous read for a topic is not allowed, we cannot send the message along
+			// via Firebase. Instead, we send a "poll_request" message, asking the client to poll.
 			data = map[string]string{
 				"id":    m.ID,
 				"time":  fmt.Sprintf("%d", m.Time),
-				"event": m.Event,
+				"event": pollRequestEvent,
 				"topic": m.Topic,
 			}
-		case messageEvent:
-			allowForward := true
-			if auther != nil {
-				allowForward = auther.Authorize(nil, m.Topic, auth.PermissionRead) == nil
-			}
-			if allowForward {
-				data = map[string]string{
-					"id":       m.ID,
-					"time":     fmt.Sprintf("%d", m.Time),
-					"event":    m.Event,
-					"topic":    m.Topic,
-					"priority": fmt.Sprintf("%d", m.Priority),
-					"tags":     strings.Join(m.Tags, ","),
-					"click":    m.Click,
-					"title":    m.Title,
-					"message":  m.Message,
-					"encoding": m.Encoding,
-				}
-				if m.Attachment != nil {
-					data["attachment_name"] = m.Attachment.Name
-					data["attachment_type"] = m.Attachment.Type
-					data["attachment_size"] = fmt.Sprintf("%d", m.Attachment.Size)
-					data["attachment_expires"] = fmt.Sprintf("%d", m.Attachment.Expires)
-					data["attachment_url"] = m.Attachment.URL
-				}
-			} else {
-				// If anonymous read for a topic is not allowed, we cannot send the message along
-				// via Firebase. Instead, we send a "poll_request" message, asking the client to poll.
-				data = map[string]string{
-					"id":    m.ID,
-					"time":  fmt.Sprintf("%d", m.Time),
-					"event": pollRequestEvent,
-					"topic": m.Topic,
-				}
-			}
 		}
-		var androidConfig *messaging.AndroidConfig
-		if m.Priority >= 4 {
-			androidConfig = &messaging.AndroidConfig{
-				Priority: "high",
-			}
+	}
+	var androidConfig *messaging.AndroidConfig
+	if m.Priority >= 4 {
+		androidConfig = &messaging.AndroidConfig{
+			Priority: "high",
 		}
-		return sender(maybeTruncateFCMMessage(&messaging.Message{
-			Topic:   m.Topic,
-			Data:    data,
-			Android: androidConfig,
-		}))
-	}, nil
+	}
+	return maybeTruncateFCMMessage(&messaging.Message{
+		Topic:   m.Topic,
+		Data:    data,
+		Android: androidConfig,
+	}), nil
 }