diff --git a/lib/interfaces/jwt-module-options.interface.ts b/lib/interfaces/jwt-module-options.interface.ts
index d5c70004..6d451c26 100644
--- a/lib/interfaces/jwt-module-options.interface.ts
+++ b/lib/interfaces/jwt-module-options.interface.ts
@@ -36,7 +36,7 @@ export interface JwtModuleAsyncOptions extends Pick<ModuleMetadata, 'imports'> {
 
 export interface JwtSignOptions extends jwt.SignOptions {
   secret?: string | Buffer;
-  privateKey?: string | Buffer;
+  privateKey?: jwt.Secret;
 }
 
 export interface JwtVerifyOptions extends jwt.VerifyOptions {