diff --git a/api/src/controllers/permission.ts b/api/src/controllers/permission.ts
index d968692..c986d81 100644
--- a/api/src/controllers/permission.ts
+++ b/api/src/controllers/permission.ts
@@ -34,10 +34,10 @@ interface RegisterPermissionPayload {
    */
   principalType: string
   /**
-   * The id of user(number), group(name), or client(clientId) to which a rule is assigned.
+   * The id of user or group to which a rule is assigned.
    * @example 123
    */
-  principalId: any
+  principalId: number
 }
 
 interface UpdatePermissionPayload {
diff --git a/api/src/utils/validation.ts b/api/src/utils/validation.ts
index a9d35c2..84a0138 100644
--- a/api/src/utils/validation.ts
+++ b/api/src/utils/validation.ts
@@ -79,7 +79,7 @@ export const registerPermissionValidation = (data: any): Joi.ValidationResult =>
     uri: Joi.string().required(),
     setting: Joi.string().required(),
     principalType: Joi.string().required(),
-    principalId: Joi.any().required()
+    principalId: Joi.number().required()
   }).validate(data)
 
 export const updatePermissionValidation = (data: any): Joi.ValidationResult =>