diff --git a/src/hdkey.ts b/src/hdkey.ts
index e39fe22..830bad8 100644
--- a/src/hdkey.ts
+++ b/src/hdkey.ts
@@ -13,7 +13,7 @@ export default class EthereumHDKey {
   /**
    * Creates an instance based on BIP39 mnemonic phrases
    */
-  public static fromMnemonic(mnemonic: string, passphrase?: string) {
+  public static fromMnemonic(mnemonic: string, passphrase?: string): EthereumHDKey {
     return EthereumHDKey.fromMasterSeed(Buffer.from(mnemonicToSeedSync(mnemonic, passphrase)))
   }