diff --git a/packages/next/build/generate-build-id.ts b/packages/next/build/generate-build-id.ts
index aed1d6c864e9a1a..af4f78763f38c5f 100644
--- a/packages/next/build/generate-build-id.ts
+++ b/packages/next/build/generate-build-id.ts
@@ -1,5 +1,5 @@
 export async function generateBuildId(
-  generate: () => string | null,
+  generate: () => string | null | Promise<string | null>,
   fallback: () => string
 ): Promise<string> {
   let buildId = await generate()
diff --git a/packages/next/server/config-shared.ts b/packages/next/server/config-shared.ts
index 36ad014accc3c6e..c372c4568b46121 100644
--- a/packages/next/server/config-shared.ts
+++ b/packages/next/server/config-shared.ts
@@ -70,7 +70,7 @@ export type NextConfig = { [key: string]: any } & {
   cleanDistDir?: boolean
   assetPrefix?: string
   useFileSystemPublicRoutes?: boolean
-  generateBuildId?: () => string | null
+  generateBuildId?: () => string | null | Promise<string | null>
   generateEtags?: boolean
   pageExtensions?: string[]
   compress?: boolean