diff --git a/amazon_transcribe_handler.go b/amazon_transcribe_handler.go
index 3052d75..705b15b 100644
--- a/amazon_transcribe_handler.go
+++ b/amazon_transcribe_handler.go
@@ -103,6 +103,10 @@ func (h *AmazonTranscribeHandler) Handle(ctx context.Context, reader io.Reader)
 				case *transcribestreamingservice.TranscriptEvent:
 					if h.OnResultFunc != nil {
 						if err := h.OnResultFunc(ctx, w, h.ChannelID, h.ConnectionID, h.LanguageCode, e.Transcript.Results); err != nil {
+							errResponse := NewSuzuErrorResponse(err.Error())
+							if err := encoder.Encode(errResponse); err != nil {
+								// TODO: ログを書く
+							}
 							w.CloseWithError(err)
 							return
 						}
diff --git a/speech_to_text_handler.go b/speech_to_text_handler.go
index 4e3fbcd..7fbe192 100644
--- a/speech_to_text_handler.go
+++ b/speech_to_text_handler.go
@@ -144,6 +144,10 @@ func (h *SpeechToTextHandler) Handle(ctx context.Context, reader io.Reader) (*io
 
 			if h.OnResultFunc != nil {
 				if err := h.OnResultFunc(ctx, w, h.ChannelID, h.ConnectionID, h.LanguageCode, resp.Results); err != nil {
+					errResponse := NewSuzuErrorResponse(err.Error())
+					if err := encoder.Encode(errResponse); err != nil {
+						// TODO: ログを書く
+					}
 					w.CloseWithError(err)
 					return
 				}