diff --git a/src/store/audio.ts b/src/store/audio.ts
index 52ed4ad0d7..5fb5111730 100644
--- a/src/store/audio.ts
+++ b/src/store/audio.ts
@@ -684,7 +684,7 @@ export const audioStore = createPartialStore<AudioStoreTypes>({
       {
         audioKey,
         morphingInfo,
-      }: { audioKey: string; morphingInfo: MorphingInfo }
+      }: { audioKey: string; morphingInfo: MorphingInfo | undefined }
     ) {
       const item = state.audioItems[audioKey];
       item.morphingInfo = morphingInfo;
@@ -2535,7 +2535,7 @@ export const audioCommandStore = transformCommandStore(
         draft,
         payload: {
           audioKey: string;
-          morphingInfo: MorphingInfo;
+          morphingInfo: MorphingInfo | undefined;
         }
       ) {
         audioStore.mutations.SET_MORPHING_INFO(draft, payload);
@@ -2544,7 +2544,7 @@ export const audioCommandStore = transformCommandStore(
         { commit },
         payload: {
           audioKey: string;
-          morphingInfo: MorphingInfo;
+          morphingInfo: MorphingInfo | undefined;
         }
       ) {
         commit("COMMAND_SET_MORPHING_INFO", payload);
diff --git a/src/store/type.ts b/src/store/type.ts
index 9d51889a6d..c170b43a51 100644
--- a/src/store/type.ts
+++ b/src/store/type.ts
@@ -269,7 +269,7 @@ export type AudioStoreTypes = {
   SET_MORPHING_INFO: {
     mutation: {
       audioKey: string;
-      morphingInfo: MorphingInfo;
+      morphingInfo: MorphingInfo | undefined;
     };
   };
 
@@ -590,9 +590,12 @@ export type AudioCommandStoreTypes = {
   COMMAND_SET_MORPHING_INFO: {
     mutation: {
       audioKey: string;
-      morphingInfo: MorphingInfo;
+      morphingInfo: MorphingInfo | undefined;
     };
-    action(payload: { audioKey: string; morphingInfo: MorphingInfo }): void;
+    action(payload: {
+      audioKey: string;
+      morphingInfo: MorphingInfo | undefined;
+    }): void;
   };
 
   COMMAND_SET_AUDIO_PRESET: {
diff --git a/src/type/preload.ts b/src/type/preload.ts
index 01d95c84f7..6f92798cf9 100644
--- a/src/type/preload.ts
+++ b/src/type/preload.ts
@@ -206,16 +206,15 @@ export type Preset = {
   volumeScale: number;
   prePhonemeLength: number;
   postPhonemeLength: number;
+  morphingInfo?: MorphingInfo;
 };
 
-export type MorphingInfo =
-  | {
-      rate: number;
-      targetEngineId: string;
-      targetSpeakerId: string;
-      targetStyleId: number;
-    }
-  | undefined;
+export type MorphingInfo = {
+  rate: number;
+  targetEngineId: string;
+  targetSpeakerId: string;
+  targetStyleId: number;
+};
 
 export type PresetConfig = {
   items: Record<string, Preset>;