diff --git a/packages/typescript-typings/types/ethers/index.d.ts b/packages/typescript-typings/types/ethers/index.d.ts
index 58bc1e8a91..875563ba2d 100644
--- a/packages/typescript-typings/types/ethers/index.d.ts
+++ b/packages/typescript-typings/types/ethers/index.d.ts
@@ -49,7 +49,7 @@ declare module 'ethers' {
     };
 
     export interface AbiCoder {
-        encode: (names?: ParamName[], types: string[], args: any[]) => string;
-        decode: (names?: ParamName[], types: string[], data: string) => any;
+        encode: (names: ParamName[] | string[], types: string[] | any[], args: any[] | undefined) => string;
+        decode: (names: ParamName[] | string[], types: string[] | string, data: string | undefined) => any;
     }
 }