diff --git a/types/webpack-sources/index.d.ts b/types/webpack-sources/index.d.ts
index 7eecb45c60..49ee96f8c7 100644
--- a/types/webpack-sources/index.d.ts
+++ b/types/webpack-sources/index.d.ts
@@ -154,7 +154,7 @@ export class ReplaceSource extends Source implements SourceAndMapMixin {
     _name: string;
     replacements: any[][];
 
-    constructor(source: Source, name: string);
+    constructor(source: Source, name?: string);
 
     replace(start: number, end: number, newValue: string): void;