diff --git a/internal/notif/base.go b/internal/notif/base.go
index 62ac650a..12ce7eea 100644
--- a/internal/notif/base.go
+++ b/internal/notif/base.go
@@ -30,7 +30,7 @@ var (
 
 // Validate implements the utils.CustomValidator interface.
 func (base *ProviderBase) Validate() gperr.Error {
-	if base.Format == nil {
+	if base.Format == nil || base.Format.string == "" {
 		base.Format = LogFormatMarkdown
 	}
 	if !strings.HasPrefix(base.URL, "http://") && !strings.HasPrefix(base.URL, "https://") {
diff --git a/internal/notif/body.go b/internal/notif/body.go
index 5edd92bb..4b797a5a 100644
--- a/internal/notif/body.go
+++ b/internal/notif/body.go
@@ -3,7 +3,6 @@ package notif
 import (
 	"bytes"
 	"encoding/json"
-	"fmt"
 	"strings"
 
 	"github.com/yusing/go-proxy/internal/gperr"
@@ -126,5 +125,5 @@ func (e ErrorBody) Format(format *LogFormat) ([]byte, error) {
 	case LogFormatMarkdown:
 		return gperr.Markdown(e.Error), nil
 	}
-	return nil, fmt.Errorf("unknown format: %v", format)
+	return gperr.Markdown(e.Error), nil
 }