diff --git a/packages/backend/src/server/api/endpoints/i/update.ts b/packages/backend/src/server/api/endpoints/i/update.ts
index 3c2f1cea0d..cdc974f5ca 100644
--- a/packages/backend/src/server/api/endpoints/i/update.ts
+++ b/packages/backend/src/server/api/endpoints/i/update.ts
@@ -105,9 +105,7 @@ export const paramDef = {
 		alwaysMarkNsfw: { type: 'boolean' },
 		autoSensitive: { type: 'boolean' },
 		ffVisibility: { type: 'string', enum: ['public', 'followers', 'private'] },
-		pinnedPageId: { type: 'array', items: {
-			type: 'string', format: 'misskey:id',
-		} },
+		pinnedPageId: { type: 'string', format: 'misskey:id', nullable: true },
 		mutedWords: { type: 'array' },
 		mutedInstances: { type: 'array', items: {
 			type: 'string',