diff --git a/CHANGELOG.md b/CHANGELOG.md
index a1dc3e2fe9..d6cb37162b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -41,6 +41,7 @@
 ### Server
 - Enhance: ノートの削除処理の効率化
 - Enhance: 全体的なパフォーマンスの向上
+- Fix: SystemWebhook設定でsecretを空に出来ない問題を修正
 
 
 ## 2025.7.0
diff --git a/packages/backend/src/server/api/endpoints/admin/system-webhook/create.ts b/packages/backend/src/server/api/endpoints/admin/system-webhook/create.ts
index 28071e7a33..93d293ed41 100644
--- a/packages/backend/src/server/api/endpoints/admin/system-webhook/create.ts
+++ b/packages/backend/src/server/api/endpoints/admin/system-webhook/create.ts
@@ -48,8 +48,8 @@ export const paramDef = {
 		},
 		secret: {
 			type: 'string',
-			minLength: 1,
 			maxLength: 1024,
+			default: '',
 		},
 	},
 	required: [
@@ -57,7 +57,6 @@ export const paramDef = {
 		'name',
 		'on',
 		'url',
-		'secret',
 	],
 } as const;
 
diff --git a/packages/backend/src/server/api/endpoints/admin/system-webhook/update.ts b/packages/backend/src/server/api/endpoints/admin/system-webhook/update.ts
index 8d68bb8f87..e021806398 100644
--- a/packages/backend/src/server/api/endpoints/admin/system-webhook/update.ts
+++ b/packages/backend/src/server/api/endpoints/admin/system-webhook/update.ts
@@ -52,8 +52,8 @@ export const paramDef = {
 		},
 		secret: {
 			type: 'string',
-			minLength: 1,
 			maxLength: 1024,
+			default: '',
 		},
 	},
 	required: [
@@ -62,7 +62,6 @@ export const paramDef = {
 		'name',
 		'on',
 		'url',
-		'secret',
 	],
 } as const;
 
diff --git a/packages/misskey-js/src/autogen/types.ts b/packages/misskey-js/src/autogen/types.ts
index 50a96174c7..f0efd63d3a 100644
--- a/packages/misskey-js/src/autogen/types.ts
+++ b/packages/misskey-js/src/autogen/types.ts
@@ -11887,7 +11887,8 @@ export interface operations {
                     name: string;
                     on: ('abuseReport' | 'abuseReportResolved' | 'userCreated' | 'inactiveModeratorsWarning' | 'inactiveModeratorsInvitationOnlyChanged')[];
                     url: string;
-                    secret: string;
+                    /** @default  */
+                    secret?: string;
                 };
             };
         };
@@ -12231,7 +12232,8 @@ export interface operations {
                     name: string;
                     on: ('abuseReport' | 'abuseReportResolved' | 'userCreated' | 'inactiveModeratorsWarning' | 'inactiveModeratorsInvitationOnlyChanged')[];
                     url: string;
-                    secret: string;
+                    /** @default  */
+                    secret?: string;
                 };
             };
         };