diff --git a/src/client.ts b/src/client.ts
index e80b148..f6915b3 100644
--- a/src/client.ts
+++ b/src/client.ts
@@ -33,7 +33,7 @@ function makeClient (app: Application, _options?: Partial<ClientOptions>): Authe
   const authManagement = app.service(path);
 
   const client: AuthenticationManagementClient = {
-    checkUnique: async (identifyUser: IdentifyUser, ownId: NullableId, ifErrMsg?: boolean) => {
+    checkUnique: async (identifyUser: IdentifyUser, ownId?: NullableId, ifErrMsg?: boolean) => {
       await authManagement.create({
         action: 'checkUnique',
         value: identifyUser,
@@ -129,7 +129,7 @@ function makeClient (app: Application, _options?: Partial<ClientOptions>): Authe
       try {
         if (!user || !user.isVerified) {
           await app.logout();
-          return cb(new Error(user ? 'User\'s email is not verified.' : 'No user returned.'));
+          return cb && cb(new Error(user ? 'User\'s email is not verified.' : 'No user returned.'));
         }
 
         if (cb) {
@@ -140,7 +140,7 @@ function makeClient (app: Application, _options?: Partial<ClientOptions>): Authe
         return user;
       } catch (err) {
         if (!cbCalled && cb) {
-          cb(err);
+          cb(err as Error);
         }
       }
     }
diff --git a/src/helpers/hash-password.ts b/src/helpers/hash-password.ts
index 4cd121f..a4501cc 100644
--- a/src/helpers/hash-password.ts
+++ b/src/helpers/hash-password.ts
@@ -7,7 +7,7 @@ export async function hashPassword (
   field: string
 ): Promise<string> {
   if (!field) throw new Error('Field is missing');
-  const context = {
+  const context: Partial<HookContext> = {
     type: 'before',
     data: { [field]: password },
     params: { provider: null },
diff --git a/src/helpers/sanitize-user-for-client.ts b/src/helpers/sanitize-user-for-client.ts
index 1fde79b..3e56fd6 100644
--- a/src/helpers/sanitize-user-for-client.ts
+++ b/src/helpers/sanitize-user-for-client.ts
@@ -2,7 +2,7 @@ import { cloneObject } from './clone-object';
 import type { User } from '../types';
 
 export function sanitizeUserForClient (
-  _user: User
+  _user: Partial<User>
 ): Record<string, unknown> {
   const user = cloneObject(_user);
 
diff --git a/src/helpers/sanitize-user-for-notifier.ts b/src/helpers/sanitize-user-for-notifier.ts
index f0ef31c..e89f0c5 100644
--- a/src/helpers/sanitize-user-for-notifier.ts
+++ b/src/helpers/sanitize-user-for-notifier.ts
@@ -1,7 +1,7 @@
 import { cloneObject } from './clone-object';
 import type { User } from '../types';
 
-export function sanitizeUserForNotifier (_user: User): Record<string, unknown> {
+export function sanitizeUserForNotifier (_user: Partial<User>): Record<string, unknown> {
   const user = cloneObject(_user);
   delete user.password;
   return user;
diff --git a/src/helpers/typescript.ts b/src/helpers/typescript.ts
new file mode 100644
index 0000000..83d0916
--- /dev/null
+++ b/src/helpers/typescript.ts
@@ -0,0 +1,3 @@
+export function typedObjectKeys<T extends object>(o: T): Array<keyof T> {
+  return Object.keys(o) as Array<keyof T>;
+}
diff --git a/src/hooks/add-verification.ts b/src/hooks/add-verification.ts
index e2b3abe..7ab4892 100644
--- a/src/hooks/add-verification.ts
+++ b/src/hooks/add-verification.ts
@@ -55,8 +55,9 @@ export function addVerification <H extends HookContext = HookContext>(
       );
 
       return context;
-    } catch (err) {
-      throw new GeneralError(err);
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    } catch (err: any) {
+      throw new GeneralError(err?.message);
     }
   };
 }
diff --git a/src/hooks/remove-verification.ts b/src/hooks/remove-verification.ts
index 2e9555e..584e01f 100644
--- a/src/hooks/remove-verification.ts
+++ b/src/hooks/remove-verification.ts
@@ -12,8 +12,8 @@ export function removeVerification <H extends HookContext = HookContext> (
   return (context: H): H => {
     checkContext(context, 'after');
     // Retrieve the items from the hook
-    const items: User | User[] = getItems(context);
-    if (!items) return;
+    const items: Partial<User> | Partial<User>[] = getItems(context);
+    if (!items) return context;
     const isArray = Array.isArray(items);
     const users = (isArray ? items : [items]);
 
diff --git a/src/methods/check-unique.ts b/src/methods/check-unique.ts
index a239dc6..6366703 100644
--- a/src/methods/check-unique.ts
+++ b/src/methods/check-unique.ts
@@ -1,6 +1,7 @@
 import { BadRequest } from '@feathersjs/errors';
 import makeDebug from 'debug';
 
+import { typedObjectKeys } from '../helpers/typescript';
 import type { NullableId, Params } from '@feathersjs/feathers';
 import type {
   CheckUniqueOptions,
@@ -33,10 +34,10 @@ export default async function checkUnique (
   } = options;
 
   const usersService = app.service(service);
-  const usersServiceId = usersService.id;
+  const usersServiceId = usersService.id!;
   const errProps = [];
 
-  const keys = Object.keys(identifyUser).filter(
+  const keys = typedObjectKeys(identifyUser).filter(
     key => identifyUser[key] != null
   );
 
@@ -59,16 +60,17 @@ export default async function checkUnique (
         errProps.push(prop);
       }
     }
-  } catch (err) {
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  } catch (err: any) {
     throw new BadRequest(
       meta?.noErrMsg ? null : 'checkUnique unexpected error.',
-      { errors: { msg: err.message, $className: 'unexpected' } }
+      { errors: { msg: err?.message, $className: 'unexpected' } }
     );
   }
 
   if (errProps.length) {
-    const errs = {};
-    errProps.forEach(prop => { errs[prop] = 'Already taken.'; });
+    const errs: Record<string, string> = {};
+    errProps.forEach((prop ) => { errs[prop] = 'Already taken.'; });
 
     throw new BadRequest(
       meta?.noErrMsg ? null : 'Values already taken.',
diff --git a/src/methods/identity-change.ts b/src/methods/identity-change.ts
index 1f2d632..2f2e746 100644
--- a/src/methods/identity-change.ts
+++ b/src/methods/identity-change.ts
@@ -31,7 +31,7 @@ export default async function identityChange (
   }
 
   const usersService = options.app.service(options.service);
-  const usersServiceId = usersService.id;
+  const usersServiceId = usersService.id!;
   const {
     delay,
     identifyUserProps,
diff --git a/src/methods/password-change.ts b/src/methods/password-change.ts
index cd76e94..14acea0 100644
--- a/src/methods/password-change.ts
+++ b/src/methods/password-change.ts
@@ -46,7 +46,7 @@ export default async function passwordChange (
   } = options;
 
   const usersService = app.service(service);
-  const usersServiceId = usersService.id;
+  const usersServiceId = usersService.id!;
 
   ensureValuesAreStrings(oldPassword, password);
   ensureObjPropsValid(identifyUser, identifyUserProps);
diff --git a/src/methods/resend-verify-signup.ts b/src/methods/resend-verify-signup.ts
index fa3e9ca..6dde4d9 100644
--- a/src/methods/resend-verify-signup.ts
+++ b/src/methods/resend-verify-signup.ts
@@ -23,7 +23,7 @@ const debug = makeDebug('authLocalMgnt:resendVerifySignup');
 export default async function resendVerifySignup (
   options: ResendVerifySignupOptions,
   identifyUser: IdentifyUser,
-  notifierOptions: NotifierOptions,
+  notifierOptions?: NotifierOptions,
   params?: Params
 ): Promise<SanitizedUser> {
   debug('identifyUser=', identifyUser);
@@ -46,7 +46,7 @@ export default async function resendVerifySignup (
   } = options;
 
   const usersService = app.service(service);
-  const usersServiceId = usersService.id;
+  const usersServiceId = usersService.id!;
 
   ensureObjPropsValid(identifyUser,
     identifyUserProps.concat('verifyToken', 'verifyShortToken')
diff --git a/src/methods/reset-password.ts b/src/methods/reset-password.ts
index 2cc3cf3..06cfe8e 100644
--- a/src/methods/reset-password.ts
+++ b/src/methods/reset-password.ts
@@ -9,6 +9,7 @@ import {
   hashPassword,
   notify
 } from '../helpers';
+import { typedObjectKeys } from '../helpers/typescript';
 import type { Id, Params } from '@feathersjs/feathers';
 
 import type {
@@ -90,7 +91,7 @@ async function resetPassword (
   } = options;
 
   const usersService = app.service(service);
-  const usersServiceId = usersService.id;
+  const usersServiceId = usersService.id!;
   let users;
 
   if (tokens.resetToken) {
@@ -114,7 +115,7 @@ async function resetPassword (
   const user = getUserData(users, checkProps);
 
   // compare all tokens (hashed)
-  const tokenChecks = Object.keys(tokens).map(async key => {
+  const tokenChecks = typedObjectKeys(tokens).map(async key => {
     if (reuseResetToken) {
       // Comparing token directly as reused resetToken is not hashed
       if (tokens[key] !== user[key]) {
@@ -124,7 +125,7 @@ async function resetPassword (
       }
     } else {
       return await comparePasswords(
-        tokens[key],
+        tokens[key]!,
         user[key] as string,
         () =>
           new BadRequest(
diff --git a/src/methods/send-reset-pwd.ts b/src/methods/send-reset-pwd.ts
index fca976b..fd0b5e4 100644
--- a/src/methods/send-reset-pwd.ts
+++ b/src/methods/send-reset-pwd.ts
@@ -51,7 +51,7 @@ export default async function sendResetPwd (
   } = options;
 
   const usersService = app.service(service);
-  const usersServiceId = usersService.id;
+  const usersServiceId = usersService.id!;
 
   ensureObjPropsValid(identifyUser, identifyUserProps);
 
diff --git a/src/methods/verify-signup-set-password.ts b/src/methods/verify-signup-set-password.ts
index 4fe8032..afbecea 100644
--- a/src/methods/verify-signup-set-password.ts
+++ b/src/methods/verify-signup-set-password.ts
@@ -8,6 +8,7 @@ import {
   isDateAfterNow,
   notify
 } from '../helpers';
+import { typedObjectKeys } from '../helpers/typescript';
 import type { Id, Params } from '@feathersjs/feathers';
 import type { VerifyChanges } from '..';
 
@@ -91,7 +92,7 @@ async function verifySignupSetPassword (
   } = options;
 
   const usersService = app.service(service);
-  const usersServiceId = usersService.id;
+  const usersServiceId = usersService.id!;
 
   const users = await usersService.find({
     ...params,
@@ -103,7 +104,7 @@ async function verifySignupSetPassword (
     'verifyNotExpired'
   ]);
 
-  if (!Object.keys(tokens).every((key) => tokens[key] === user[key])) {
+  if (!typedObjectKeys(tokens).every((key) => tokens[key] === user[key])) {
     await eraseVerifyProps(user, user.isVerified, params);
 
     throw new BadRequest(
diff --git a/src/methods/verify-signup.ts b/src/methods/verify-signup.ts
index eec904d..ab4b74a 100644
--- a/src/methods/verify-signup.ts
+++ b/src/methods/verify-signup.ts
@@ -7,6 +7,7 @@ import {
   notify,
   isDateAfterNow
 } from '../helpers';
+import { typedObjectKeys } from '../helpers/typescript';
 import type { Id, Params } from '@feathersjs/feathers';
 
 import type {
@@ -82,7 +83,7 @@ async function verifySignup (
   } = options;
 
   const usersService = app.service(service);
-  const usersServiceId = usersService.id;
+  const usersServiceId = usersService.id!;
 
   const users = await usersService.find(
     {
@@ -98,7 +99,7 @@ async function verifySignup (
 
   let userErasedVerify: User;
 
-  if (!Object.keys(tokens).every(key => tokens[key] === user[key])) {
+  if (!typedObjectKeys(tokens).every((key) => tokens[key] === user[key])) {
     userErasedVerify = await eraseVerifyProps(user, user.isVerified);
 
     throw new BadRequest(
diff --git a/src/options.ts b/src/options.ts
index 0b1db37..334695d 100644
--- a/src/options.ts
+++ b/src/options.ts
@@ -14,7 +14,7 @@ export const defaultPath = 'authManagement';
 export const optionsDefault: AuthenticationManagementServiceOptions = {
   service: '/users', // need exactly this for test suite
   // eslint-disable-next-line @typescript-eslint/no-unused-vars, @typescript-eslint/no-empty-function
-  notifier: async (type: NotificationType, user: User, notifierOptions) => {},
+  notifier: async (type: NotificationType, user: Partial<User>, notifierOptions) => {},
   longTokenLen: 15, // token's length will be twice this
   shortTokenLen: 6,
   shortTokenDigits: true,
diff --git a/src/services/AuthenticationManagementBase.ts b/src/services/AuthenticationManagementBase.ts
index 09a9993..6be13c9 100644
--- a/src/services/AuthenticationManagementBase.ts
+++ b/src/services/AuthenticationManagementBase.ts
@@ -1,9 +1,12 @@
+/* eslint-disable @typescript-eslint/no-explicit-any */
 import { MethodNotAllowed } from '@feathersjs/errors';
 import type { Application, Params } from '@feathersjs/feathers';
 
 export abstract class AuthenticationManagementBase<T, R, O> {
-  publish: unknown;
+  publish: undefined | ((fn: ((...any: any[]) => unknown)) => void);
   app: Application;
+  // eslint-disable-next-line @typescript-eslint/ban-ts-comment
+  // @ts-ignore not defined in constructor but is used.
   options: O;
 
   abstract _create (data: T, params?: Params): Promise<R>;
@@ -31,7 +34,7 @@ export abstract class AuthenticationManagementBase<T, R, O> {
   }
 
   async setup (): Promise<void> {
-    if (typeof this.publish === 'function') {
+    if (typeof this.publish === 'function') { 
       this.publish(() => null);
     }
   }
diff --git a/src/types.ts b/src/types.ts
index a77fecc..6981094 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -116,7 +116,7 @@ export interface AuthenticationManagementServiceOptions {
    * @default 'password' */
   passwordField: string
   /** Pass params from f-a-m service to `/users` service */
-  passParams: (params) => Params | Promise<Params>
+  passParams?: (params: any) => Params | Promise<Params>
 }
 
 export type AuthenticationManagementSetupOptions = AuthenticationManagementServiceOptions & { path: string };
diff --git a/tsconfig.json b/tsconfig.json
index b0bc86a..d0f0fe3 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -10,6 +10,7 @@
     "sourceMap": false,
     "declaration": true,
     "strictNullChecks": false,
+    "noImplicitAny": true,
   },
   "include": [
     "src/**/*"