diff --git a/packages/next/server/config-schema.ts b/packages/next/server/config-schema.ts
index 984d0df6b77d75e..6c06e28a48b3980 100644
--- a/packages/next/server/config-schema.ts
+++ b/packages/next/server/config-schema.ts
@@ -253,7 +253,14 @@ const configSchema = {
           type: 'boolean',
         },
         esmExternals: {
-          type: 'boolean',
+          oneOf: [
+            {
+              type: 'boolean',
+            },
+            {
+              const: 'loose',
+            },
+          ] as any,
         },
         externalDir: {
           type: 'boolean',