diff --git a/types/nodemailer/lib/sendmail-transport/le-unix.d.ts b/types/nodemailer/lib/sendmail-transport/le-unix.d.ts
index 2d2e203958..5f5a3bb25d 100644
--- a/types/nodemailer/lib/sendmail-transport/le-unix.d.ts
+++ b/types/nodemailer/lib/sendmail-transport/le-unix.d.ts
@@ -1,7 +1,7 @@
 /// <reference types="node" />
 
-import { Duplex } from 'stream';
+import { Transform } from 'stream';
 
-declare class LeUnix extends Duplex {}
+declare class LeUnix extends Transform {}
 
 export = LeUnix;
diff --git a/types/nodemailer/lib/sendmail-transport/le-windows.d.ts b/types/nodemailer/lib/sendmail-transport/le-windows.d.ts
index 3af80a5fb6..67ab01ff43 100644
--- a/types/nodemailer/lib/sendmail-transport/le-windows.d.ts
+++ b/types/nodemailer/lib/sendmail-transport/le-windows.d.ts
@@ -1,7 +1,7 @@
 /// <reference types="node" />
 
-import { Duplex } from 'stream';
+import { Transform } from 'stream';
 
-declare class LeWindows extends Duplex {}
+declare class LeWindows extends Transform {}
 
 export = LeWindows;