diff --git a/src/models/actions/update/UpdatePermission.ts b/src/models/actions/update/UpdatePermission.ts
index e591e20..7803398 100644
--- a/src/models/actions/update/UpdatePermission.ts
+++ b/src/models/actions/update/UpdatePermission.ts
@@ -1,7 +1,7 @@
 import { IsInt, IsNotEmpty, IsObject } from 'class-validator';
 import { getConnectionManager } from 'typeorm';
 import { PermissionNeedsPrincipalError } from '../../../errors/PermissionErrors';
-import { PrincipalNotFoundError, PrincipalWrongTypeError } from '../../../errors/PrincipalErrors';
+import { PrincipalNotFoundError } from '../../../errors/PrincipalErrors';
 import { Permission } from '../../entities/Permission';
 import { Principal } from '../../entities/Principal';
 import { PermissionAction } from '../../enums/PermissionAction';
@@ -20,12 +20,11 @@ export class UpdatePermission {
     id: number;
 
     /**
-     * The updated permissions's principal.
-     * Just has to contain the principal's id -everything else won't be checked or changed.
+     * The updated permissions's principal's id.
      */
     @IsObject()
     @IsNotEmpty()
-    principal: Principal;
+    principal: number;
 
     /**
      * The permissions's target.
@@ -57,12 +56,8 @@ export class UpdatePermission {
         if (this.principal === undefined || this.principal === null) {
             throw new PermissionNeedsPrincipalError();
         }
-        if (!isNaN(this.principal.id)) {
-            let principal = await getConnectionManager().get().getRepository(Principal).findOne({ id: this.principal.id });
-            if (!principal) { throw new PrincipalNotFoundError(); }
-            return principal;
-        }
-
-        throw new PrincipalWrongTypeError();
+        let principal = await getConnectionManager().get().getRepository(Principal).findOne({ id: this.principal });
+        if (!principal) { throw new PrincipalNotFoundError(); }
+        return principal;
     }
 }
\ No newline at end of file