diff --git a/src/storageWrappers/AsyncStorageWrapper.ts b/src/storageWrappers/AsyncStorageWrapper.ts
index 3eeb4da9..c8ef5809 100644
--- a/src/storageWrappers/AsyncStorageWrapper.ts
+++ b/src/storageWrappers/AsyncStorageWrapper.ts
@@ -12,23 +12,29 @@ import { PersistentStorage } from '../types';
  * });
  *
  */
-export class AsyncStorageWrapper implements PersistentStorage<string> {
-  // Actual type definition: https://github.com/react-native-async-storage/async-storage/blob/master/types/index.d.ts
+export class AsyncStorageWrapper implements PersistentStorage<string | null> {
   private storage;
 
-  constructor(storage: any) {
+  constructor(storage: AsyncStorageInterface) {
     this.storage = storage;
   }
 
-  getItem(key: string): string | Promise<string | null> | null {
+  getItem(key: string): Promise<string | null> {
     return this.storage.getItem(key);
   }
 
-  removeItem(key: string): void | Promise<void> {
+  removeItem(key: string): Promise<void> {
     return this.storage.removeItem(key);
   }
 
-  setItem(key: string, value: string): void | Promise<void> {
+  setItem(key: string, value: string | null): Promise<void> {
     return this.storage.setItem(key, value);
   }
 }
+
+interface AsyncStorageInterface {
+  // Actual type definition: https://github.com/react-native-async-storage/async-storage/blob/master/types/index.d.ts
+  getItem(key: string): Promise<string | null>;
+  setItem(key: string, value: string | null): Promise<void>;
+  removeItem(key: string): Promise<void>;
+}
diff --git a/src/storageWrappers/IonicStorageWrapper.ts b/src/storageWrappers/IonicStorageWrapper.ts
index 27ed0244..f9bb0c7b 100644
--- a/src/storageWrappers/IonicStorageWrapper.ts
+++ b/src/storageWrappers/IonicStorageWrapper.ts
@@ -1,22 +1,28 @@
 import { PersistentStorage } from '../types';
 
-export class IonicStorageWrapper implements PersistentStorage<string> {
-  // Actual type definition: https://github.com/ionic-team/ionic-storage/blob/main/src/storage.ts#L102
+export class IonicStorageWrapper implements PersistentStorage<string | null> {
   private storage;
 
-  constructor(storage: any) {
+  constructor(storage: IonicStorageInterface) {
     this.storage = storage;
   }
 
-  getItem(key: string): string | Promise<string | null> | null {
+  getItem(key: string): Promise<string | null> {
     return this.storage.get(key);
   }
 
-  removeItem(key: string): void | Promise<void> {
+  removeItem(key: string): Promise<void> {
     return this.storage.remove(key);
   }
 
-  setItem(key: string, value: string): void | Promise<void> {
+  setItem(key: string, value: string | null): Promise<void> {
     return this.storage.set(key, value);
   }
 }
+
+interface IonicStorageInterface {
+  // Actual type definition: https://github.com/ionic-team/ionic-storage/blob/main/lib/src/index.ts
+  get(key: string): Promise<string | null>;
+  set(key: string, value: string | null): Promise<void>;
+  remove(key: string): Promise<void>;
+}
diff --git a/src/storageWrappers/LocalForageWrapper.ts b/src/storageWrappers/LocalForageWrapper.ts
index 19e988ab..1c3e24e9 100644
--- a/src/storageWrappers/LocalForageWrapper.ts
+++ b/src/storageWrappers/LocalForageWrapper.ts
@@ -1,22 +1,22 @@
 import { PersistentStorage } from '../types';
 
-export class LocalForageWrapper implements PersistentStorage<string | object> {
-  // Actual type definition: https://github.com/localForage/localForage/blob/master/typings/localforage.d.ts#L17
+export class LocalForageWrapper
+  implements PersistentStorage<string | object | null> {
   private storage;
 
-  constructor(storage: any) {
+  constructor(storage: LocalForageInterface) {
     this.storage = storage;
   }
 
-  getItem(key: string): string | Promise<string | null> | null {
+  getItem(key: string): Promise<string | null> {
     return this.storage.getItem(key);
   }
 
-  removeItem(key: string): void | Promise<void> {
+  removeItem(key: string): Promise<void> {
     return this.storage.removeItem(key);
   }
 
-  setItem(key: string, value: string): void | Promise<void> {
+  setItem(key: string, value: string | object | null): Promise<void> {
     return new Promise((resolve, reject) => {
       this.storage
         .setItem(key, value)
@@ -25,3 +25,10 @@ export class LocalForageWrapper implements PersistentStorage<string | object> {
     });
   }
 }
+
+interface LocalForageInterface {
+  // Actual type definition: https://github.com/localForage/localForage/blob/master/typings/localforage.d.ts#L17
+  getItem(key: string): Promise<string | null>;
+  setItem(key: string, value: string | object | null): Promise<void>;
+  removeItem(key: string): Promise<void>;
+}
diff --git a/src/storageWrappers/LocalStorageWrapper.ts b/src/storageWrappers/LocalStorageWrapper.ts
index 5fb8ea8e..6238608c 100644
--- a/src/storageWrappers/LocalStorageWrapper.ts
+++ b/src/storageWrappers/LocalStorageWrapper.ts
@@ -1,22 +1,33 @@
 import { PersistentStorage } from '../types';
 
-export class LocalStorageWrapper implements PersistentStorage<string> {
-  // Actual type definition: https://github.com/microsoft/TypeScript/blob/master/lib/lib.dom.d.ts#L15286
+export class LocalStorageWrapper implements PersistentStorage<string | null> {
   private storage;
 
-  constructor(storage: any) {
+  constructor(storage: LocalStorageInterface) {
     this.storage = storage;
   }
 
-  getItem(key: string): string | Promise<string | null> | null {
+  getItem(key: string): string | null {
     return this.storage.getItem(key);
   }
 
-  removeItem(key: string): void | Promise<void> {
+  removeItem(key: string): void {
     return this.storage.removeItem(key);
   }
 
-  setItem(key: string, value: string): void | Promise<void> {
-    return this.storage.setItem(key, value);
+  setItem(key: string, value: string | null): void {
+    if (value !== null) {
+      // setting null to localstorage stores "null" as string
+      return this.storage.setItem(key, value);
+    } else {
+      return this.removeItem(key);
+    }
   }
 }
+
+interface LocalStorageInterface {
+  // Actual type definition: https://github.com/microsoft/TypeScript/blob/main/lib/lib.dom.d.ts#L14276
+  getItem(key: string): string | null;
+  setItem(key: string, value: string): void;
+  removeItem(key: string): void;
+}
diff --git a/src/storageWrappers/MMKVStorageWrapper.ts b/src/storageWrappers/MMKVStorageWrapper.ts
index ef983b04..5f6409fd 100644
--- a/src/storageWrappers/MMKVStorageWrapper.ts
+++ b/src/storageWrappers/MMKVStorageWrapper.ts
@@ -11,28 +11,30 @@ import { PersistentStorage } from '../types';
  * });
  *
  */
-export class MMKVStorageWrapper implements PersistentStorage<string> {
-  // Actual type definition: https://github.com/ammarahm-ed/react-native-mmkv-storage/blob/master/index.d.ts#L27
+export class MMKVStorageWrapper
+  implements PersistentStorage<string | null | undefined> {
   private storage;
 
-  constructor(storage: any) {
+  constructor(storage: MMKVStorageInterface) {
     this.storage = storage;
   }
 
-  getItem(key: string): string | Promise<string | null> | null {
+  getItem(key: string): Promise<string | null | undefined> {
     return this.storage.getItem(key);
   }
 
-  removeItem(key: string): void | Promise<void> {
+  removeItem(key: string): Promise<void> {
     return new Promise((resolve, reject) => {
-      this.storage
-        .removeItem(key)
+      // Ensure the removeItem is thenable, even if it's not, by wrapping it to Promise.resolve
+      // The MMKV storage's removeItem is synchronous since 0.5.7, this Promise wrap allows backward compatibility
+      // https://stackoverflow.com/a/27746324/2078771
+      Promise.resolve(this.storage.removeItem(key))
         .then(() => resolve())
         .catch(() => reject());
     });
   }
 
-  setItem(key: string, value: string): void | Promise<void> {
+  setItem(key: string, value: string | null | undefined): Promise<void> {
     return new Promise((resolve, reject) => {
       this.storage
         .setItem(key, value)
@@ -41,3 +43,10 @@ export class MMKVStorageWrapper implements PersistentStorage<string> {
     });
   }
 }
+
+interface MMKVStorageInterface {
+  // Actual type definition: https://github.com/ammarahm-ed/react-native-mmkv-storage/blob/master/index.d.ts#L27
+  getItem(key: string): Promise<string | null | undefined>;
+  setItem(key: string, value: string): Promise<boolean | undefined>;
+  removeItem(key: string): boolean | undefined | Promise<boolean | undefined>;
+}
diff --git a/src/storageWrappers/SessionStorageWrapper.ts b/src/storageWrappers/SessionStorageWrapper.ts
index 2b5ebf0d..fd1bb303 100644
--- a/src/storageWrappers/SessionStorageWrapper.ts
+++ b/src/storageWrappers/SessionStorageWrapper.ts
@@ -1,22 +1,33 @@
 import { PersistentStorage } from '../types';
 
-export class SessionStorageWrapper implements PersistentStorage<string> {
-  // Actual type definition: https://github.com/microsoft/TypeScript/blob/master/lib/lib.dom.d.ts#L15286
+export class SessionStorageWrapper implements PersistentStorage<string | null> {
   private storage;
 
-  constructor(storage: any) {
+  constructor(storage: SessionStorageInterface) {
     this.storage = storage;
   }
 
-  getItem(key: string): string | Promise<string | null> | null {
+  getItem(key: string): string | null {
     return this.storage.getItem(key);
   }
 
-  removeItem(key: string): void | Promise<void> {
+  removeItem(key: string): void {
     return this.storage.removeItem(key);
   }
 
-  setItem(key: string, value: string): void | Promise<void> {
-    return this.storage.setItem(key, value);
+  setItem(key: string, value: string | null): void {
+    if (value !== null) {
+      // setting null to sessionstorage stores "null" as string
+      return this.storage.setItem(key, value);
+    } else {
+      return this.removeItem(key);
+    }
   }
 }
+
+interface SessionStorageInterface {
+  // Actual type definition: https://github.com/microsoft/TypeScript/blob/main/lib/lib.dom.d.ts#L14276
+  getItem(key: string): string | null;
+  setItem(key: string, value: string): void;
+  removeItem(key: string): void;
+}