diff --git a/crates/next-core/src/next_config.rs b/crates/next-core/src/next_config.rs
index ef603e73460d3d..8deef01e40a05b 100644
--- a/crates/next-core/src/next_config.rs
+++ b/crates/next-core/src/next_config.rs
@@ -141,10 +141,6 @@ pub struct NextConfig {
     compress: bool,
     eslint: EslintConfig,
     exclude_default_moment_locales: bool,
-    // this can be a function in js land
-    export_path_map: Option<serde_json::Value>,
-    // this is a function in js land
-    generate_build_id: Option<serde_json::Value>,
     generate_etags: bool,
     http_agent_options: HttpAgentConfig,
     on_demand_entries: OnDemandEntriesConfig,
@@ -156,7 +152,11 @@ pub struct NextConfig {
     typescript: TypeScriptConfig,
     use_file_system_public_routes: bool,
     cache_components: Option<bool>,
-    webpack: Option<serde_json::Value>,
+    //
+    // These are never used by Turbopack, and potentially non-serializable anyway:
+    // export_path_map: Option<serde_json::Value>,
+    // generate_build_id: Option<serde_json::Value>,
+    // webpack: Option<serde_json::Value>,
 }
 
 #[turbo_tasks::value_impl]
diff --git a/packages/next/src/build/swc/index.ts b/packages/next/src/build/swc/index.ts
index c0ff835a8f49a8..cd8b2dfaa33b2d 100644
--- a/packages/next/src/build/swc/index.ts
+++ b/packages/next/src/build/swc/index.ts
@@ -852,11 +852,10 @@ function bindingToApi(
     // Avoid mutating the existing `nextConfig` object. NOTE: This is only a shallow clone.
     let nextConfigSerializable: Record<string, any> = { ...nextConfig }
 
-    nextConfigSerializable.generateBuildId =
-      await nextConfigSerializable.generateBuildId?.()
-
-    // TODO: these functions takes arguments, have to be supported in a different way
+    // These values are never read by Turbopack and are potentially non-serializable.
     nextConfigSerializable.exportPathMap = {}
+    nextConfigSerializable.generateBuildId =
+      nextConfigSerializable.generateBuildId && {}
     nextConfigSerializable.webpack = nextConfigSerializable.webpack && {}
 
     if (nextConfigSerializable.modularizeImports) {