diff --git a/src/type/s2k/argon2.ts b/src/type/s2k/argon2.ts
index 5636d608..f8421b57 100644
--- a/src/type/s2k/argon2.ts
+++ b/src/type/s2k/argon2.ts
@@ -2,6 +2,8 @@ import defaultConfig from '../../config';
 import enums from '../../enums';
 import util from '../../util';
 import crypto from '../../crypto';
+import type { default as loadArgonWasmModuleType } from 'argon2id';
+import { Config } from '../../../openpgp';
 
 const ARGON2_TYPE = 0x02; // id
 const ARGON2_VERSION = 0x13;
@@ -20,21 +22,21 @@ export class Argon2OutOfMemoryError extends Error {
 }
 
 // cache argon wasm module
-let loadArgonWasmModule: Function;
-let argon2Promise: Promise<Function>;
+let loadArgonWasmModule: typeof loadArgonWasmModuleType;
+let argon2Promise: ReturnType<typeof loadArgonWasmModuleType>;
 // reload wasm module above this treshold, to deallocated used memory
 const ARGON2_WASM_MEMORY_THRESHOLD_RELOAD = 2 << 19;
 
 class Argon2S2K {
-    type: string;
-    salt: Uint8Array | null;
-    t: number;
-    p: number;
-    encodedM: number;
+    type: 'argon2';
+    private salt: Uint8Array | null;
+    private t: number;
+    private p: number;
+    private encodedM: number;
   /**
   * @param {Object} [config] - Full configuration, defaults to openpgp.config
   */
-  constructor(config = defaultConfig) {
+  constructor(config: Config) {
     
     const { passes, parallelism, memoryExponent } = config.s2kArgon2Params;
 
diff --git a/src/type/s2k/generic.ts b/src/type/s2k/generic.ts
index df6bc8ea..36b9b41b 100644
--- a/src/type/s2k/generic.ts
+++ b/src/type/s2k/generic.ts
@@ -27,9 +27,10 @@
  * @module type/s2k
  */
 
-import defaultConfig from '../../config';
-import crypto from '../../crypto';
+import type { Config, enums as enumsType } from '../../../openpgp';
 import enums from '../../enums';
+
+import crypto from '../../crypto';
 import { UnsupportedError } from '../../packet/packet';
 import util from '../../util';
 
@@ -41,7 +42,7 @@ class GenericS2K {
   /**
    * @param {Object} [config] - Full configuration, defaults to openpgp.config
    */
-  constructor(s2kType: number, config = defaultConfig) {
+  constructor(s2kType: enumsType.s2k.simple | enumsType.s2k.salted | enumsType.s2k.iterated, config: Config) {
     /**
      * Hash function identifier, or 0 for gnu-dummy keys
      * @type {module:enums.hash | 0}
diff --git a/src/type/s2k/index.ts b/src/type/s2k/index.ts
index 2948cfbb..7fd8059a 100644
--- a/src/type/s2k/index.ts
+++ b/src/type/s2k/index.ts
@@ -1,9 +1,9 @@
-import defaultConfig from '../../config';
 import Argon2S2K, { Argon2OutOfMemoryError } from './argon2';
 import GenericS2K from './generic';
 import enums from '../../enums';
 import { UnsupportedError } from '../../packet/packet';
 import GnuS2K from './gnu';
+import { Config } from '../../../openpgp';
 
 const allowedS2KTypesForEncryption = new Set([enums.s2k.argon2, enums.s2k.iterated]);
 
@@ -14,7 +14,7 @@ const allowedS2KTypesForEncryption = new Set([enums.s2k.argon2, enums.s2k.iterat
  * @returns {Object} New s2k object
  * @throws {Error} for unknown or unsupported types
  */
-export function newS2KFromType (type: number, config = defaultConfig): Argon2S2K | GenericS2K | GnuS2K {
+export function newS2KFromType (type: number, config: Config): Argon2S2K | GenericS2K | GnuS2K {
   switch (type) {
     case enums.s2k.gnu:
       return new GnuS2K();
@@ -35,7 +35,7 @@ export function newS2KFromType (type: number, config = defaultConfig): Argon2S2K
  * @returns {Object} New s2k object
  * @throws {Error} for unknown or unsupported types
  */
-export function newS2KFromConfig(config = defaultConfig) {
+export function newS2KFromConfig(config: Config) {
   const { s2kType } = config;
 
   if (!allowedS2KTypesForEncryption.has(s2kType)) {