diff --git a/.eslintignore b/.eslintignore
index 002420d13..d79232c44 100644
--- a/.eslintignore
+++ b/.eslintignore
@@ -61,7 +61,6 @@ Modules/TinyMCE/IconPack/postinstall.js
 Modules/TinyMCE/langs/
 
 # AUTO-GENERATED - EXCLUDED TYPESCRIPT BUILD
-CliClient/tests/synchronizer_LockHandler.js
 ElectronClient/commands/focusElement.js
 ElectronClient/commands/startExternalEditing.js
 ElectronClient/commands/stopExternalEditing.js
@@ -155,7 +154,6 @@ ReactNativeClient/lib/services/ResourceEditWatcher.js
 ReactNativeClient/lib/services/rest/actionApi.desktop.js
 ReactNativeClient/lib/services/rest/errors.js
 ReactNativeClient/lib/services/SettingUtils.js
-ReactNativeClient/lib/services/synchronizer/LockHandler.js
 ReactNativeClient/lib/services/UndoRedoService.js
 ReactNativeClient/lib/ShareExtension.js
 ReactNativeClient/lib/shareHandler.js
diff --git a/.gitignore b/.gitignore
index c3d4bcb02..b08e40c5a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -51,7 +51,6 @@ Tools/commit_hook.txt
 *.map
 
 # AUTO-GENERATED - EXCLUDED TYPESCRIPT BUILD
-CliClient/tests/synchronizer_LockHandler.js
 ElectronClient/commands/focusElement.js
 ElectronClient/commands/startExternalEditing.js
 ElectronClient/commands/stopExternalEditing.js
@@ -145,7 +144,6 @@ ReactNativeClient/lib/services/ResourceEditWatcher.js
 ReactNativeClient/lib/services/rest/actionApi.desktop.js
 ReactNativeClient/lib/services/rest/errors.js
 ReactNativeClient/lib/services/SettingUtils.js
-ReactNativeClient/lib/services/synchronizer/LockHandler.js
 ReactNativeClient/lib/services/UndoRedoService.js
 ReactNativeClient/lib/ShareExtension.js
 ReactNativeClient/lib/shareHandler.js
diff --git a/CliClient/gulpfile.js b/CliClient/gulpfile.js
index 2dc7c5d3f..191e81dfe 100644
--- a/CliClient/gulpfile.js
+++ b/CliClient/gulpfile.js
@@ -37,8 +37,6 @@ tasks.buildTests = {
 				'lib/',
 				'locales/',
 				'node_modules/',
-				'*.ts',
-				'*.tsx',
 			],
 		});
 
diff --git a/CliClient/tests/synchronizer.js b/CliClient/tests/synchronizer.js
index 629da5436..edcfec69d 100644
--- a/CliClient/tests/synchronizer.js
+++ b/CliClient/tests/synchronizer.js
@@ -33,7 +33,7 @@ async function allNotesFolders() {
 }
 
 async function remoteItemsByTypes(types) {
-	const list = await fileApi().list('', { includeDirs: false });
+	const list = await fileApi().list();
 	if (list.has_more) throw new Error('Not implemented!!!');
 	const files = list.items;
 
@@ -822,7 +822,7 @@ describe('synchronizer', function() {
 		// First create a folder, without encryption enabled, and sync it
 		const folder1 = await Folder.save({ title: 'folder1' });
 		await synchronizer().start();
-		let files = await fileApi().list('', { includeDirs: false });
+		let files = await fileApi().list();
 		let content = await fileApi().get(files.items[0].path);
 		expect(content.indexOf('folder1') >= 0).toBe(true);
 
@@ -1662,22 +1662,22 @@ describe('synchronizer', function() {
 		expect(hasThrown).toBe(true);
 	}));
 
-	// it('should not sync when target is locked', asyncTest(async () => {
-	// 	await synchronizer().start();
-	// 	await synchronizer().acquireLock_();
+	it('should not sync when target is locked', asyncTest(async () => {
+		await synchronizer().start();
+		await synchronizer().acquireLock_();
 
-	// 	await switchClient(2);
-	// 	const hasThrown = await checkThrowAsync(async () => synchronizer().start({ throwOnError: true }));
-	// 	expect(hasThrown).toBe(true);
-	// }));
+		await switchClient(2);
+		const hasThrown = await checkThrowAsync(async () => synchronizer().start({ throwOnError: true }));
+		expect(hasThrown).toBe(true);
+	}));
 
-	// it('should clear a lock if it was created by the same app as the current one', asyncTest(async () => {
-	// 	await synchronizer().start();
-	// 	await synchronizer().acquireLock_();
-	// 	expect((await synchronizer().lockFiles_()).length).toBe(1);
-	// 	await synchronizer().start({ throwOnError: true });
-	// 	expect((await synchronizer().lockFiles_()).length).toBe(0);
-	// }));
+	it('should clear a lock if it was created by the same app as the current one', asyncTest(async () => {
+		await synchronizer().start();
+		await synchronizer().acquireLock_();
+		expect((await synchronizer().lockFiles_()).length).toBe(1);
+		await synchronizer().start({ throwOnError: true });
+		expect((await synchronizer().lockFiles_()).length).toBe(0);
+	}));
 
 	it('should not encrypt notes that are shared', asyncTest(async () => {
 		Setting.setValue('encryption.enabled', true);
diff --git a/CliClient/tests/synchronizer_LockHandler.ts b/CliClient/tests/synchronizer_LockHandler.ts
deleted file mode 100644
index 1e2dbf974..000000000
--- a/CliClient/tests/synchronizer_LockHandler.ts
+++ /dev/null
@@ -1,104 +0,0 @@
-import LockHandler, { LockType } from 'lib/services/synchronizer/LockHandler';
-
-require('app-module-path').addPath(__dirname);
-
-const { asyncTest, fileApi, setupDatabaseAndSynchronizer, switchClient, msleep, expectThrow, expectNotThrow } = require('test-utils.js');
-
-process.on('unhandledRejection', (reason:any, p:any) => {
-	console.log('Unhandled Rejection at: Promise', p, 'reason:', reason);
-});
-
-let lockHandler_:LockHandler = null;
-const locksDirname = 'locks';
-
-function lockHandler():LockHandler {
-	if (lockHandler_) return lockHandler_;
-	lockHandler_ = new LockHandler(fileApi(), locksDirname);
-	return lockHandler_;
-}
-
-describe('synchronizer_LockHandler', function() {
-
-	beforeEach(async (done:Function) => {
-		lockHandler_ = null;
-		await setupDatabaseAndSynchronizer(1);
-		await setupDatabaseAndSynchronizer(2);
-		await switchClient(1);
-		done();
-	});
-
-	it('should acquire and release a sync lock', asyncTest(async () => {
-		await lockHandler().acquireLock(LockType.Sync, 'mobile', '123456');
-		const locks = await lockHandler().syncLocks();
-		expect(locks.length).toBe(1);
-		expect(locks[0].type).toBe(LockType.Sync);
-		expect(locks[0].clientId).toBe('123456');
-		expect(locks[0].clientType).toBe('mobile');
-
-		await lockHandler().releaseLock(LockType.Sync, 'mobile', '123456');
-		expect((await lockHandler().syncLocks()).length).toBe(0);
-	}));
-
-	it('should allow multiple sync locks', asyncTest(async () => {
-		await lockHandler().acquireLock(LockType.Sync, 'mobile', '111');
-
-		await switchClient(2);
-
-		await lockHandler().acquireLock(LockType.Sync, 'mobile', '222');
-
-		expect((await lockHandler().syncLocks()).length).toBe(2);
-
-		{
-			await lockHandler().releaseLock(LockType.Sync, 'mobile', '222');
-			const locks = await lockHandler().syncLocks();
-			expect(locks.length).toBe(1);
-			expect(locks[0].clientId).toBe('111');
-		}
-	}));
-
-	it('should refresh sync lock timestamp when acquiring again', asyncTest(async () => {
-		await lockHandler().acquireLock(LockType.Sync, 'mobile', '111');
-
-		const beforeTime = (await lockHandler().syncLocks())[0].updatedTime;
-		await msleep(1);
-
-		await lockHandler().acquireLock(LockType.Sync, 'mobile', '111');
-
-		const afterTime = (await lockHandler().syncLocks())[0].updatedTime;
-
-		expect(beforeTime).toBeLessThan(afterTime);
-	}));
-
-	it('should not allow sync locks if there is an exclusive lock', asyncTest(async () => {
-		await lockHandler().acquireLock(LockType.Exclusive, 'desktop', '111');
-
-		expectThrow(async () => {
-			await lockHandler().acquireLock(LockType.Sync, 'mobile', '222');
-		}, 'hasExclusiveLock');
-	}));
-
-	it('should not allow exclusive lock if there are sync locks', asyncTest(async () => {
-		lockHandler().syncLockMaxAge = 1000 * 60 * 60;
-
-		await lockHandler().acquireLock(LockType.Sync, 'mobile', '111');
-		await lockHandler().acquireLock(LockType.Sync, 'mobile', '222');
-
-		expectThrow(async () => {
-			await lockHandler().acquireLock(LockType.Exclusive, 'desktop', '333');
-		}, 'hasSyncLock');
-	}));
-
-	it('should allow exclusive lock if the sync locks have expired', asyncTest(async () => {
-		lockHandler().syncLockMaxAge = 1;
-
-		await lockHandler().acquireLock(LockType.Sync, 'mobile', '111');
-		await lockHandler().acquireLock(LockType.Sync, 'mobile', '222');
-
-		await msleep(2);
-
-		expectNotThrow(async () => {
-			await lockHandler().acquireLock(LockType.Exclusive, 'desktop', '333');
-		});
-	}));
-
-});
diff --git a/CliClient/tests/test-utils.js b/CliClient/tests/test-utils.js
index 14cb666d5..c1450e1eb 100644
--- a/CliClient/tests/test-utils.js
+++ b/CliClient/tests/test-utils.js
@@ -132,14 +132,6 @@ function sleep(n) {
 	});
 }
 
-function msleep(ms) {
-	return new Promise((resolve, reject) => {
-		setTimeout(() => {
-			resolve();
-		}, ms);
-	});
-}
-
 function currentClientId() {
 	return currentClient_;
 }
@@ -386,40 +378,6 @@ async function checkThrowAsync(asyncFn) {
 	return hasThrown;
 }
 
-async function expectThrow(asyncFn, errorCode = undefined) {
-	let hasThrown = false;
-	let thrownErrorCode = null;
-	try {
-		await asyncFn();
-	} catch (error) {
-		hasThrown = true;
-		thrownErrorCode = error.code;
-	}
-
-	if (!hasThrown) {
-		expect('not throw').toBe('throw', 'Expected function to throw an error but did not');
-	} else if (thrownErrorCode !== errorCode) {
-		expect(`error code: ${thrownErrorCode}`).toBe(`error code: ${errorCode}`);
-	} else {
-		expect(true).toBe(true);
-	}
-}
-
-async function expectNotThrow(asyncFn) {
-	let thrownError = null;
-	try {
-		await asyncFn();
-	} catch (error) {
-		thrownError = error;
-	}
-
-	if (thrownError) {
-		expect(thrownError.message).toBe('', 'Expected function not to throw an error but it did');
-	} else {
-		expect(true).toBe(true);
-	}
-}
-
 function checkThrow(fn) {
 	let hasThrown = false;
 	try {
@@ -457,7 +415,7 @@ function asyncTest(callback) {
 }
 
 async function allSyncTargetItemsEncrypted() {
-	const list = await fileApi().list('', { includeDirs: false });
+	const list = await fileApi().list();
 	const files = list.items;
 
 	let totalCount = 0;
@@ -615,4 +573,4 @@ class TestApp extends BaseApplication {
 	}
 }
 
-module.exports = { kvStore, expectThrow, expectNotThrow, resourceService, resourceFetcher, tempFilePath, allSyncTargetItemsEncrypted, msleep, setupDatabase, revisionService, setupDatabaseAndSynchronizer, db, synchronizer, fileApi, sleep, clearDatabase, switchClient, syncTargetId, objectsEqual, checkThrowAsync, checkThrow, encryptionService, loadEncryptionMasterKey, fileContentEqual, decryptionWorker, asyncTest, currentClientId, id, ids, sortedIds, at, createNTestNotes, createNTestFolders, createNTestTags, TestApp };
+module.exports = { kvStore, resourceService, resourceFetcher, tempFilePath, allSyncTargetItemsEncrypted, setupDatabase, revisionService, setupDatabaseAndSynchronizer, db, synchronizer, fileApi, sleep, clearDatabase, switchClient, syncTargetId, objectsEqual, checkThrowAsync, checkThrow, encryptionService, loadEncryptionMasterKey, fileContentEqual, decryptionWorker, asyncTest, currentClientId, id, ids, sortedIds, at, createNTestNotes, createNTestFolders, createNTestTags, TestApp };
diff --git a/ElectronClient/package-lock.json b/ElectronClient/package-lock.json
index a73d641ba..0af931858 100644
--- a/ElectronClient/package-lock.json
+++ b/ElectronClient/package-lock.json
@@ -235,12 +235,6 @@
       "integrity": "sha512-Q1y515GcOdTHgagaVFhHnIFQ38ygs/kmxdNpvpou+raI9UO3YZcHDngBSYKQklcKlvA7iuQlmIKbzvmxcOE9CQ==",
       "dev": true
     },
-    "@types/jasmine": {
-      "version": "3.5.11",
-      "resolved": "https://registry.npmjs.org/@types/jasmine/-/jasmine-3.5.11.tgz",
-      "integrity": "sha512-fg1rOd/DehQTIJTifGqGVY6q92lDgnLfs7C6t1ccSwQrMyoTGSoH6wWzhJDZb6ezhsdwAX4EIBLe8w5fXWmEng==",
-      "dev": true
-    },
     "@types/node": {
       "version": "12.12.38",
       "resolved": "https://registry.npmjs.org/@types/node/-/node-12.12.38.tgz",
diff --git a/ElectronClient/package.json b/ElectronClient/package.json
index d21db08f1..6e365eada 100644
--- a/ElectronClient/package.json
+++ b/ElectronClient/package.json
@@ -79,7 +79,6 @@
   },
   "homepage": "https://github.com/laurent22/joplin#readme",
   "devDependencies": {
-    "@types/jasmine": "^3.5.11",
     "ajv": "^6.5.0",
     "app-builder-bin": "^1.9.11",
     "babel-cli": "^6.26.0",
diff --git a/ReactNativeClient/lib/file-api-driver-memory.js b/ReactNativeClient/lib/file-api-driver-memory.js
index 568ef3aab..762a81e0c 100644
--- a/ReactNativeClient/lib/file-api-driver-memory.js
+++ b/ReactNativeClient/lib/file-api-driver-memory.js
@@ -111,7 +111,7 @@ class FileApiDriverMemory {
 			this.items_.push(item);
 		} else {
 			this.items_[index].content = this.encodeContent_(content);
-			this.items_[index].updated_time = time.unixMs();
+			this.items_[index].updated_time = time.unix();
 		}
 	}
 
diff --git a/ReactNativeClient/lib/file-api-driver-webdav.js b/ReactNativeClient/lib/file-api-driver-webdav.js
index ace44635a..f43ec498d 100644
--- a/ReactNativeClient/lib/file-api-driver-webdav.js
+++ b/ReactNativeClient/lib/file-api-driver-webdav.js
@@ -89,7 +89,7 @@ class FileApiDriverWebDav {
 
 	async delta(path, options) {
 		const getDirStats = async path => {
-			const result = await this.list(path, { includeDirs: false });
+			const result = await this.list(path);
 			return result.items;
 		};
 
diff --git a/ReactNativeClient/lib/file-api.js b/ReactNativeClient/lib/file-api.js
index 6f545720f..754960090 100644
--- a/ReactNativeClient/lib/file-api.js
+++ b/ReactNativeClient/lib/file-api.js
@@ -128,7 +128,6 @@ class FileApi {
 		if (!options) options = {};
 		if (!('includeHidden' in options)) options.includeHidden = false;
 		if (!('context' in options)) options.context = null;
-		if (!('includeDirs' in options)) options.includeDirs = true;
 
 		this.logger().debug(`list ${this.baseDir()}`);
 
@@ -142,10 +141,6 @@ class FileApi {
 			result.items = temp;
 		}
 
-		if (!options.includeHidden) {
-			result.items = result.items.filter(f => !f.isDir);
-		}
-
 		return result;
 	}
 
diff --git a/ReactNativeClient/lib/services/synchronizer/LockHandler.ts b/ReactNativeClient/lib/services/synchronizer/LockHandler.ts
deleted file mode 100644
index bbacaa773..000000000
--- a/ReactNativeClient/lib/services/synchronizer/LockHandler.ts
+++ /dev/null
@@ -1,220 +0,0 @@
-const JoplinError = require('lib/JoplinError');
-const { time } = require('lib/time-utils');
-const { fileExtension, filename } = require('lib/path-utils.js');
-
-export enum LockType {
-	None = '',
-	Sync = 'sync',
-	Exclusive = 'exclusive',
-}
-
-export interface Lock {
-	type: LockType,
-	clientType: string,
-	clientId: string,
-	updatedTime?: number,
-}
-
-const exclusiveFilename = 'exclusive.json';
-
-export default class LockHandler {
-
-	private api_:any = null;
-	private lockDirPath_:any = null;
-	private syncLockMaxAge_:number = 1000 * 60 * 3;
-
-	constructor(api:any, lockDirPath:string) {
-		this.api_ = api;
-		this.lockDirPath_ = lockDirPath;
-	}
-
-	public get syncLockMaxAge():number {
-		return this.syncLockMaxAge_;
-	}
-
-	// Should only be done for testing purposes since all clients should
-	// use the same lock max age.
-	public set syncLockMaxAge(v:number) {
-		this.syncLockMaxAge_ = v;
-	}
-
-	private lockFilename(lock:Lock) {
-		if (lock.type === LockType.Exclusive) {
-			return exclusiveFilename;
-		} else {
-			return `${[lock.type, lock.clientType, lock.clientId].join('_')}.json`;
-		}
-	}
-
-	private lockTypeFromFilename(name:string):LockType {
-		if (name === exclusiveFilename) return LockType.Exclusive;
-		return LockType.Sync;
-	}
-
-	private lockFilePath(lock:Lock) {
-		return `${this.lockDirPath_}/${this.lockFilename(lock)}`;
-	}
-
-	private exclusiveFilePath():string {
-		return `${this.lockDirPath_}/${exclusiveFilename}`;
-	}
-
-	private syncLockFileToObject(file:any):Lock {
-		const p = filename(file.path).split('_');
-
-		return {
-			type: p[0],
-			clientType: p[1],
-			clientId: p[2],
-			updatedTime: file.updated_time,
-		};
-	}
-
-	async syncLocks():Promise<Lock[]> {
-		const result = await this.api_.list(this.lockDirPath_);
-		if (result.hasMore) throw new Error('hasMore not handled'); // Shouldn't happen anyway
-
-		const output = [];
-		for (const file of result.items) {
-			const ext = fileExtension(file.path);
-			if (ext !== 'json') continue;
-
-			const type = this.lockTypeFromFilename(file.path);
-			if (type !== LockType.Sync) continue;
-
-			const lock = this.syncLockFileToObject(file);
-			output.push(lock);
-		}
-
-		return output;
-	}
-
-	private async exclusiveLock():Promise<Lock> {
-		const stat = await this.api_.stat(this.exclusiveFilePath());
-		if (!stat) return null;
-
-		const contentText = await this.api_.get(this.exclusiveFilePath());
-		if (!contentText) return null; // race condition
-
-		const lock:Lock = JSON.parse(contentText) as Lock;
-		lock.updatedTime = stat.updated_time;
-		return lock;
-	}
-
-	private lockIsActive(lock:Lock):boolean {
-		return Date.now() - lock.updatedTime < this.syncLockMaxAge;
-	}
-
-	async hasActiveExclusiveLock():Promise<boolean> {
-		const lock = await this.exclusiveLock();
-		return !!lock && this.lockIsActive(lock);
-	}
-
-	async hasActiveSyncLock(clientType:string, clientId:string) {
-		const locks = await this.syncLocks();
-		for (const lock of locks) {
-			if (lock.clientType === clientType && lock.clientId === clientId && this.lockIsActive(lock)) return true;
-		}
-		return false;
-	}
-
-	private async saveLock(lock:Lock) {
-		await this.api_.put(this.lockFilePath(lock), JSON.stringify(lock));
-	}
-
-	private async acquireSyncLock(clientType:string, clientId:string) {
-		const exclusiveLock = await this.exclusiveLock();
-
-		if (exclusiveLock) {
-			throw new JoplinError(`Cannot acquire sync lock because the following client has an exclusive lock on the sync target: ${this.lockToClientString(exclusiveLock)}`, 'hasExclusiveLock');
-		}
-
-		await this.saveLock({
-			type: LockType.Sync,
-			clientType: clientType,
-			clientId: clientId,
-		});
-	}
-
-	private lockToClientString(lock:Lock):string {
-		return `(${lock.clientType} #${lock.clientId})`;
-	}
-
-	private async acquireExclusiveLock(clientType:string, clientId:string, timeoutMs:number = 0) {
-		// The logic to acquire an exclusive lock, while avoiding race conditions is as follow:
-		//
-		// - Check if there is a lock file present
-		//
-		// - If there is a lock file, see if I'm the one owning it by checking that its content has my identifier.
-		// - If that's the case, just write to the data file then delete the lock file.
-		// - If that's not the case, just wait a second or a small random length of time and try the whole cycle again-.
-		//
-		// -If there is no lock file, create one with my identifier and try the whole cycle again to avoid race condition (re-check that the lock file is really mine)-.
-
-		const startTime = Date.now();
-
-		async function waitForTimeout() {
-			if (!timeoutMs) return false;
-
-			const elapsed = Date.now() - startTime;
-			if (timeoutMs && elapsed < timeoutMs) {
-				await time.sleep(2);
-				return true;
-			}
-			return false;
-		}
-
-		while (true) {
-			const syncLocks = await this.syncLocks();
-			const activeSyncLocks = syncLocks.filter(lock => this.lockIsActive(lock));
-
-			if (activeSyncLocks.length) {
-				if (await waitForTimeout()) continue;
-				const lockString = activeSyncLocks.map(l => this.lockToClientString(l)).join(', ');
-				throw new JoplinError(`Cannot acquire exclusive lock because the following clients have a sync lock on the target: ${lockString}`, 'hasSyncLock');
-			}
-
-			const exclusiveLock = await this.exclusiveLock();
-
-			if (exclusiveLock) {
-				if (exclusiveLock.clientId === clientId) {
-					// Save it again to refresh the timestamp
-					await this.saveLock(exclusiveLock);
-					return;
-				} else {
-					// If there's already an exclusive lock, wait for it to be released
-					if (await waitForTimeout()) continue;
-					throw new JoplinError(`Cannot acquire exclusive lock because the following client has an exclusive lock on the sync target: ${this.lockToClientString(exclusiveLock)}`, 'hasExclusiveLock');
-				}
-			} else {
-				// If there's not already an exclusive lock, acquire one
-				// then loop again to check that we really got the lock
-				// (to prevent race conditions)
-				await this.saveLock({
-					type: LockType.Exclusive,
-					clientType: clientType,
-					clientId: clientId,
-				});
-			}
-		}
-	}
-
-	async acquireLock(lockType:LockType, clientType:string, clientId:string, timeoutMs:number = 0) {
-		if (lockType === LockType.Sync) {
-			await this.acquireSyncLock(clientType, clientId);
-		} else if (lockType === LockType.Exclusive) {
-			await this.acquireExclusiveLock(clientType, clientId, timeoutMs);
-		} else {
-			throw new Error(`Invalid lock type: ${lockType}`);
-		}
-	}
-
-	async releaseLock(lockType:LockType, clientType:string, clientId:string) {
-		await this.api_.delete(this.lockFilePath({
-			type: lockType,
-			clientType: clientType,
-			clientId: clientId,
-		}));
-	}
-
-}
diff --git a/ReactNativeClient/lib/synchronizer.js b/ReactNativeClient/lib/synchronizer.js
index 01a2f5867..56e7f08ac 100644
--- a/ReactNativeClient/lib/synchronizer.js
+++ b/ReactNativeClient/lib/synchronizer.js
@@ -12,11 +12,10 @@ const { time } = require('lib/time-utils.js');
 const { Logger } = require('lib/logger.js');
 const { _ } = require('lib/locale.js');
 const { shim } = require('lib/shim.js');
-// const { filename, fileExtension } = require('lib/path-utils');
+const { filename, fileExtension } = require('lib/path-utils');
 const JoplinError = require('lib/JoplinError');
 const BaseSyncTarget = require('lib/BaseSyncTarget');
 const TaskQueue = require('lib/TaskQueue');
-const LockHandler = require('lib/services/synchronizer/LockHandler').default;
 
 class Synchronizer {
 	constructor(db, api, appType) {
@@ -24,7 +23,7 @@ class Synchronizer {
 		this.db_ = db;
 		this.api_ = api;
 		this.syncDirName_ = '.sync';
-		this.lockDirName_ = 'locks';
+		this.lockDirName_ = '.lock';
 		this.resourceDirName_ = BaseSyncTarget.resourceDirName();
 		this.logger_ = new Logger();
 		this.appType_ = appType;
@@ -67,12 +66,6 @@ class Synchronizer {
 		return this.logger_;
 	}
 
-	lockHandler() {
-		if (this.lockHandler_) return this.lockHandler_;
-		this.lockHandler_ = new LockHandler(this.api(), this.lockDirName_);
-		return this.lockHandler_;
-	}
-
 	maxResourceSize() {
 		if (this.maxResourceSize_ !== null) return this.maxResourceSize_;
 		return this.appType_ === 'mobile' ? 10 * 1000 * 1000 : Infinity;
@@ -212,17 +205,64 @@ class Synchronizer {
 		return state;
 	}
 
+	async acquireLock_() {
+		await this.checkLock_();
+		await this.api().put(`${this.lockDirName_}/${this.clientId()}_${Date.now()}.lock`, `${Date.now()}`);
+	}
+
+	async releaseLock_() {
+		const lockFiles = await this.lockFiles_();
+		for (const lockFile of lockFiles) {
+			const p = this.parseLockFilePath(lockFile.path);
+			if (p.clientId === this.clientId()) {
+				await this.api().delete(p.fullPath);
+			}
+		}
+	}
+
+	async lockFiles_() {
+		const output = await this.api().list(this.lockDirName_);
+		return output.items.filter((p) => {
+			const ext = fileExtension(p.path);
+			return ext === 'lock';
+		});
+	}
+
+	parseLockFilePath(path) {
+		const splitted = filename(path).split('_');
+		const fullPath = `${this.lockDirName_}/${path}`;
+		if (splitted.length !== 2) throw new Error(`Sync target appears to be locked but lock filename is invalid: ${fullPath}. Please delete it on the sync target to continue.`);
+		return {
+			clientId: splitted[0],
+			timestamp: Number(splitted[1]),
+			fullPath: fullPath,
+		};
+	}
+
+	async checkLock_() {
+		const lockFiles = await this.lockFiles_();
+		if (lockFiles.length) {
+			const lock = this.parseLockFilePath(lockFiles[0].path);
+
+			if (lock.clientId === this.clientId()) {
+				await this.releaseLock_();
+			} else {
+				throw new Error(`The sync target was locked by client ${lock.clientId} on ${time.unixMsToLocalDateTime(lock.timestamp)} and cannot be accessed. If no app is currently operating on the sync target, you can delete the files in the "${this.lockDirName_}" directory on the sync target to resume.`);
+			}
+		}
+	}
+
 	async checkSyncTargetVersion_() {
 		const supportedSyncTargetVersion = Setting.value('syncVersion');
-		const syncTargetVersion = await this.apiCall('get', '.sync/version.txt');
+		const syncTargetVersion = await this.api().get('.sync/version.txt');
 
 		if (!syncTargetVersion) {
-			await this.apiCall('put', '.sync/version.txt', `${supportedSyncTargetVersion}`);
+			await this.api().put('.sync/version.txt', `${supportedSyncTargetVersion}`);
 		} else {
 			if (Number(syncTargetVersion) > supportedSyncTargetVersion) {
 				throw new Error(sprintf('Sync version of the target (%d) does not match sync version supported by client (%d). Please upgrade your client.', Number(syncTargetVersion), supportedSyncTargetVersion));
 			} else {
-				await this.apiCall('put', '.sync/version.txt', `${supportedSyncTargetVersion}`);
+				await this.api().put('.sync/version.txt', `${supportedSyncTargetVersion}`);
 				// TODO: do upgrade job
 			}
 		}
@@ -232,44 +272,6 @@ class Synchronizer {
 		return steps.includes('update_remote') && steps.includes('delete_remote') && steps.includes('delta');
 	}
 
-	async lockErrorStatus_() {
-		const hasActiveExclusiveLock = await this.lockHandler().hasActiveExclusiveLock();
-		if (hasActiveExclusiveLock) return 'hasExclusiveLock';
-
-		const hasActiveSyncLock = await this.lockHandler().hasActiveSyncLock();
-		if (!hasActiveSyncLock) return 'syncLockGone';
-
-		return '';
-	}
-
-	async apiCall(fnName, ...args) {
-		if (this.syncTargetIsLocked_) throw new JoplinError('Sync target is locked - aborting API call', 'lockError');
-
-		try {
-			const output = await this.api()[fnName](...args);
-			return output;
-		} catch (error) {
-			const lockStatus = await this.lockErrorStatus_();
-			// When there's an error due to a lock, we re-wrap the error and change the error code so that error handling
-			// does not do special processing on the original error. For example, if a resource could not be downloaded,
-			// don't mark it as a "cannotSyncItem" since we don't know that.
-			if (lockStatus) {
-				throw new JoplinError(`Sync target lock error: ${lockStatus}. Original error was: ${error.message}`, 'lockError');
-			} else {
-				throw error;
-			}
-		}
-	}
-
-	async refreshLock() {
-		if (this.state_ !== 'in_progress') {
-			this.logger().warn('Trying to refresh lock, but sync is not in progress');
-			return;
-		}
-
-		await this.lockHandler().acquireLock('sync', this.appType_, this.clientId_);
-	}
-
 	// Synchronisation is done in three major steps:
 	//
 	// 1. UPLOAD: Send to the sync target the items that have changed since the last sync.
@@ -298,7 +300,6 @@ class Synchronizer {
 
 		const syncTargetId = this.api().syncTargetId();
 
-		this.syncTargetIsLocked_ = false;
 		this.cancelling_ = false;
 
 		const masterKeysBefore = await MasterKey.count();
@@ -324,27 +325,12 @@ class Synchronizer {
 		let errorToThrow = null;
 
 		try {
-			await this.apiCall('mkdir', this.syncDirName_);
-			await this.apiCall('mkdir', this.lockDirName_);
+			await this.api().mkdir(this.syncDirName_);
+			await this.api().mkdir(this.lockDirName_);
 			this.api().setTempDirName(this.syncDirName_);
-			await this.apiCall('mkdir', this.resourceDirName_);
-
-			await this.lockHandler().acquireLock('sync', this.appType_, this.clientId_);
-
-			if (this.refreshLockIID_) clearInterval(this.refreshLockIID_);
-
-			this.refreshLockIID_ = setInterval(async () => {
-				try {
-					await this.refreshLock();
-				} catch (error) {
-					this.logger().warn('Could not refresh lock - cancelling sync. Error was:', error);
-					clearInterval(this.refreshLockIID_);
-					this.syncTargetIsLocked_ = true;
-					this.refreshLockIID_ = null;
-					this.cancel();
-				}
-			}, 1000 * 60);
+			await this.api().mkdir(this.resourceDirName_);
 
+			await this.checkLock_();
 			await this.checkSyncTargetVersion_();
 
 			// ========================================================================
@@ -383,7 +369,7 @@ class Synchronizer {
 						//   (by setting an updated_time less than current time).
 						if (donePaths.indexOf(path) >= 0) throw new JoplinError(sprintf('Processing a path that has already been done: %s. sync_time was not updated? Remote item has an updated_time in the future?', path), 'processingPathTwice');
 
-						const remote = await this.apiCall('stat', path);
+						const remote = await this.api().stat(path);
 						let action = null;
 
 						let reason = '';
@@ -421,7 +407,7 @@ class Synchronizer {
 							// OneDrive does not appear to have accurate timestamps as lastModifiedDateTime would occasionally be
 							// a few seconds ahead of what it was set with setTimestamp()
 							try {
-								remoteContent = await this.apiCall('get', path);
+								remoteContent = await this.api().get(path);
 							} catch (error) {
 								if (error.code === 'rejectedByTarget') {
 									this.progressReport_.errors.push(error);
@@ -464,7 +450,7 @@ class Synchronizer {
 										this.logger().warn(`Uploading a large resource (resourceId: ${local.id}, size:${local.size} bytes) which may tie up the sync process.`);
 									}
 
-									await this.apiCall('put', remoteContentPath, null, { path: localResourceContentPath, source: 'file' });
+									await this.api().put(remoteContentPath, null, { path: localResourceContentPath, source: 'file' });
 								} catch (error) {
 									if (error && ['rejectedByTarget', 'fileNotFound'].indexOf(error.code) >= 0) {
 										await handleCannotSyncItem(ItemClass, syncTargetId, local, error.message);
@@ -481,7 +467,7 @@ class Synchronizer {
 							try {
 								if (this.testingHooks_.indexOf('notesRejectedByTarget') >= 0 && local.type_ === BaseModel.TYPE_NOTE) throw new JoplinError('Testing rejectedByTarget', 'rejectedByTarget');
 								const content = await ItemClass.serializeForSync(local);
-								await this.apiCall('put', path, content);
+								await this.api().put(path, content);
 							} catch (error) {
 								if (error && error.code === 'rejectedByTarget') {
 									await handleCannotSyncItem(ItemClass, syncTargetId, local, error.message);
@@ -607,11 +593,11 @@ class Synchronizer {
 					const item = deletedItems[i];
 					const path = BaseItem.systemPath(item.item_id);
 					this.logSyncOperation('deleteRemote', null, { id: item.item_id }, 'local has been deleted');
-					await this.apiCall('delete', path);
+					await this.api().delete(path);
 
 					if (item.item_type === BaseModel.TYPE_RESOURCE) {
 						const remoteContentPath = resourceRemotePath(item.item_id);
-						await this.apiCall('delete', remoteContentPath);
+						await this.api().delete(remoteContentPath);
 					}
 
 					await BaseItem.remoteDeletedItem(syncTargetId, item.item_id);
@@ -642,7 +628,7 @@ class Synchronizer {
 				while (true) {
 					if (this.cancelling() || hasCancelled) break;
 
-					const listResult = await this.apiCall('delta', '', {
+					const listResult = await this.api().delta('', {
 						context: context,
 
 						// allItemIdsHandler() provides a way for drivers that don't have a delta API to
@@ -667,7 +653,7 @@ class Synchronizer {
 						if (this.cancelling()) break;
 
 						this.downloadQueue_.push(remote.path, async () => {
-							return this.apiCall('get', remote.path);
+							return this.api().get(remote.path);
 						});
 					}
 
@@ -683,7 +669,7 @@ class Synchronizer {
 						if (!BaseItem.isSystemPath(remote.path)) continue; // The delta API might return things like the .sync, .resource or the root folder
 
 						const loadContent = async () => {
-							const task = await this.downloadQueue_.waitForResult(path); // await this.apiCall('get', path);
+							const task = await this.downloadQueue_.waitForResult(path); // await this.api().get(path);
 							if (task.error) throw task.error;
 							if (!task.result) return null;
 							return await BaseItem.unserialize(task.result);
@@ -846,13 +832,13 @@ class Synchronizer {
 		} catch (error) {
 			if (throwOnError) {
 				errorToThrow = error;
-			} else if (error && ['cannotEncryptEncrypted', 'noActiveMasterKey', 'processingPathTwice', 'failSafe', 'lockError'].indexOf(error.code) >= 0) {
+			} else if (error && ['cannotEncryptEncrypted', 'noActiveMasterKey', 'processingPathTwice', 'failSafe'].indexOf(error.code) >= 0) {
 				// Only log an info statement for this since this is a common condition that is reported
 				// in the application, and needs to be resolved by the user.
 				// Or it's a temporary issue that will be resolved on next sync.
 				this.logger().info(error.message);
 
-				if (error.code === 'failSafe' || error.code === 'lockError') {
+				if (error.code === 'failSafe') {
 					// Get the message to display on UI, but not in testing to avoid poluting stdout
 					if (!shim.isTestingEnv()) this.progressReport_.errors.push(error.message);
 					this.logLastRequests();
@@ -871,15 +857,6 @@ class Synchronizer {
 			}
 		}
 
-		await this.lockHandler().releaseLock('sync', this.appType_, this.clientId_);
-
-		if (this.refreshLockIID_) {
-			clearInterval(this.refreshLockIID_);
-			this.refreshLockIID_ = null;
-		}
-
-		this.syncTargetIsLocked_ = false;
-
 		if (this.cancelling()) {
 			this.logger().info('Synchronisation was cancelled.');
 			this.cancelling_ = false;
diff --git a/package-lock.json b/package-lock.json
index 704cebd70..0a20d7b8c 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -92,12 +92,6 @@
         "hoist-non-react-statics": "^3.3.0"
       }
     },
-    "@types/jasmine": {
-      "version": "3.5.11",
-      "resolved": "https://registry.npmjs.org/@types/jasmine/-/jasmine-3.5.11.tgz",
-      "integrity": "sha512-fg1rOd/DehQTIJTifGqGVY6q92lDgnLfs7C6t1ccSwQrMyoTGSoH6wWzhJDZb6ezhsdwAX4EIBLe8w5fXWmEng==",
-      "dev": true
-    },
     "@types/json-schema": {
       "version": "7.0.3",
       "resolved": "https://registry.npmjs.org/@types/json-schema/-/json-schema-7.0.3.tgz",
@@ -4195,22 +4189,6 @@
       "resolved": "https://registry.npmjs.org/isstream/-/isstream-0.1.2.tgz",
       "integrity": "sha1-R+Y/evVa+m+S4VAOaQ64uFKcCZo="
     },
-    "jasmine": {
-      "version": "3.5.0",
-      "resolved": "https://registry.npmjs.org/jasmine/-/jasmine-3.5.0.tgz",
-      "integrity": "sha512-DYypSryORqzsGoMazemIHUfMkXM7I7easFaxAvNM3Mr6Xz3Fy36TupTrAOxZWN8MVKEU5xECv22J4tUQf3uBzQ==",
-      "dev": true,
-      "requires": {
-        "glob": "^7.1.4",
-        "jasmine-core": "~3.5.0"
-      }
-    },
-    "jasmine-core": {
-      "version": "3.5.0",
-      "resolved": "https://registry.npmjs.org/jasmine-core/-/jasmine-core-3.5.0.tgz",
-      "integrity": "sha512-nCeAiw37MIMA9w9IXso7bRaLl+c/ef3wnxsoSAlYrzS+Ot0zTG6nU8G/cIfGkqpkjX2wNaIW9RFG0TwIFnG6bA==",
-      "dev": true
-    },
     "joplin-turndown": {
       "version": "4.0.28",
       "resolved": "https://registry.npmjs.org/joplin-turndown/-/joplin-turndown-4.0.28.tgz",
diff --git a/package.json b/package.json
index 9f648a49e..e5d89cd0f 100644
--- a/package.json
+++ b/package.json
@@ -20,7 +20,6 @@
   },
   "license": "MIT",
   "devDependencies": {
-    "@types/jasmine": "^3.5.11",
     "@types/react": "^16.9.0",
     "@types/react-dom": "^16.9.0",
     "@types/react-redux": "^7.1.7",
@@ -34,7 +33,6 @@
     "glob": "^7.1.6",
     "gulp": "^4.0.2",
     "husky": "^3.0.2",
-    "jasmine": "^3.5.0",
     "lint-staged": "^9.2.1",
     "typescript": "^3.7.3"
   },
diff --git a/tsconfig.json b/tsconfig.json
index e63bd4340..fb3bf0186 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -15,10 +15,6 @@
 		"sourceMap": true,
 		"jsx": "react",
 		"skipLibCheck": true,
-		"baseUrl": ".",
-		"paths": {
-			"lib/*": ["./ReactNativeClient/lib/*"],
-		},
 	},
     "include": [
         "ReactNativeClient/**/*",