diff --git a/packages/helpers/src/lib/mailauth/tools.ts b/packages/helpers/src/lib/mailauth/tools.ts
index 3b0b2298..53a9395d 100644
--- a/packages/helpers/src/lib/mailauth/tools.ts
+++ b/packages/helpers/src/lib/mailauth/tools.ts
@@ -24,16 +24,13 @@ const keyOrderingDKIM = ['v', 'a', 'c', 'd', 'h', 'i', 'l', 'q', 's', 't', 'x',
 
 export const writeToStream = async (
   stream: DkimVerifier,
-  input: Buffer & { pipe: (...args: any) => void; on: (...args: any) => void },
+  input: Buffer & NodeJS.ReadableStream,
   chunkSize: number = 0,
 ) => {
   chunkSize = chunkSize || 64 * 1024;
 
   if (typeof input === 'string') {
-    input = Buffer.from(input) as Buffer & {
-      pipe: (...args: any) => void;
-      on: (...args: any) => void;
-    };
+    input = Buffer.from(input) as Buffer & NodeJS.ReadableStream;
   }
 
   return new Promise((resolve, reject) => {
diff --git a/packages/helpers/src/sha-utils.ts b/packages/helpers/src/sha-utils.ts
index c74bb65f..16501c84 100644
--- a/packages/helpers/src/sha-utils.ts
+++ b/packages/helpers/src/sha-utils.ts
@@ -19,7 +19,7 @@ export function findIndexInUint8Array(array: Uint8Array, selector: Uint8Array):
   return -1;
 }
 
-export function padUint8ArrayWithZeros(array: Uint8Array, length: number) {
+export function padUint8ArrayWithZeros(array: Uint8Array, length: number): Uint8Array {
   while (array.length < length) {
     // eslint-disable-next-line no-param-reassign
     array = mergeUInt8Arrays(array, int8toBytes(0));