diff --git a/byline/byline.d.ts b/byline/byline.d.ts
index 6dac6ad50b..475386b28c 100644
--- a/byline/byline.d.ts
+++ b/byline/byline.d.ts
@@ -9,7 +9,7 @@ declare module "byline" {
     import stream = require("stream");
 
     export interface LineStreamOptions extends stream.TransformOptions {
-        keepEmptyLines: boolean;
+        keepEmptyLines?: boolean;
     }
 
     export interface LineStream extends stream.Transform {
@@ -35,4 +35,4 @@ declare module "byline" {
     export function createStream(stream:NodeJS.ReadableStream, options?:LineStreamOptions):LineStream;
 
     export var LineStream:LineStreamCreatable;
-}
\ No newline at end of file
+}