diff --git a/types/jsonld/index.d.ts b/types/jsonld/index.d.ts
index 8ec02cd360..1c24273663 100644
--- a/types/jsonld/index.d.ts
+++ b/types/jsonld/index.d.ts
@@ -117,9 +117,9 @@ export function expand(input: Document, options: Options.Expand, callback: DocCa
 export function expand(input: Document, callback: DocCallback): void;
 export function expand(input: Document, options?: Options.Expand): Promise<JsonLd>;
 
-export function flatten(input: Document, ctx: Context, options: Options.Flatten, callback: DocCallback): void;
-export function flatten(input: Document, ctx: Context, callback: DocCallback): void;
-export function flatten(input: Document, ctx: Context, options?: Options.Flatten): Promise<JsonLd>;
+export function flatten(input: Document, ctx: Context|null, options: Options.Flatten, callback: DocCallback): void;
+export function flatten(input: Document, ctx: Context|null, callback: DocCallback): void;
+export function flatten(input: Document, ctx: Context|null, options?: Options.Flatten): Promise<JsonLd>;
 
 export function frame(input: Document, frame: Document, options: Options.Frame, callback: DocCallback): void;
 export function frame(input: Document, frame: Document, callback: DocCallback): void;