diff --git a/build/gulpfile.extensions.js b/build/gulpfile.extensions.js
index c7591abc6c6da..1d0ac3da216a7 100644
--- a/build/gulpfile.extensions.js
+++ b/build/gulpfile.extensions.js
@@ -47,11 +47,7 @@ const tasks = compilations.map(function (tsconfigFile) {
 	const clean = 'clean-extension:' + name;
 	const compile = 'compile-extension:' + name;
 	const watch = 'watch-extension:' + name;
-
-	// Build Tasks
-	const cleanBuild = 'clean-extension-build:' + name;
 	const compileBuild = 'compile-extension-build:' + name;
-	const watchBuild = 'watch-extension-build:' + name;
 
 	const root = path.join('extensions', relativeDirname);
 	const srcBase = path.join(root, 'src');
@@ -112,15 +108,18 @@ const tasks = compilations.map(function (tsconfigFile) {
 	const srcOpts = { cwd: path.dirname(__dirname), base: srcBase };
 
 	gulp.task(clean, cb => rimraf(out, cb));
+	const cleanTask = () => util.primraf(out);
 
-	gulp.task(compile, [clean], () => {
+	gulp.task(compile, util.taskSeries(cleanTask, () => {
 		const pipeline = createPipeline(false, true);
 		const input = gulp.src(src, srcOpts);
 
-		return input
+		return util.streamToPromise(
+			input
 			.pipe(pipeline())
-			.pipe(gulp.dest(out));
-	});
+			.pipe(gulp.dest(out))
+		);
+	}));
 
 	gulp.task(watch, [clean], () => {
 		const pipeline = createPipeline(false);
@@ -132,39 +131,24 @@ const tasks = compilations.map(function (tsconfigFile) {
 			.pipe(gulp.dest(out));
 	});
 
-	gulp.task(cleanBuild, cb => rimraf(out, cb));
-
-	gulp.task(compileBuild, [clean], () => {
+	gulp.task(compileBuild, util.taskSeries(cleanTask, () => {
 		const pipeline = createPipeline(true, true);
 		const input = gulp.src(src, srcOpts);
 
-		return input
+		return util.streamToPromise(
+			input
 			.pipe(pipeline())
-			.pipe(gulp.dest(out));
-	});
-
-	gulp.task(watchBuild, [clean], () => {
-		const pipeline = createPipeline(true);
-		const input = gulp.src(src, srcOpts);
-		const watchInput = watcher(src, srcOpts);
-
-		return watchInput
-			.pipe(util.incremental(() => pipeline(), input))
-			.pipe(gulp.dest(out));
-	});
+			.pipe(gulp.dest(out))
+		);
+	}));
 
 	return {
-		clean: clean,
 		compile: compile,
 		watch: watch,
-		cleanBuild: cleanBuild,
-		compileBuild: compileBuild,
-		watchBuild: watchBuild
+		compileBuild: compileBuild
 	};
 });
 
 gulp.task('compile-extensions', tasks.map(t => t.compile));
 gulp.task('watch-extensions', tasks.map(t => t.watch));
-
 gulp.task('compile-extensions-build', tasks.map(t => t.compileBuild));
-gulp.task('watch-extensions-build', tasks.map(t => t.watchBuild));
diff --git a/build/lib/util.js b/build/lib/util.js
index e6f041f3d60d8..a03adac0f37e4 100644
--- a/build/lib/util.js
+++ b/build/lib/util.js
@@ -183,6 +183,39 @@ function rimraf(dir) {
     return cb => retry(cb);
 }
 exports.rimraf = rimraf;
+/**
+ * Like rimraf (with 5 retries), but with a promise instead of a callback.
+ */
+function primraf(dir) {
+    const fn = rimraf(dir);
+    return new Promise((resolve, reject) => {
+        fn((err) => {
+            if (err) {
+                return reject(err);
+            }
+            resolve();
+        });
+    });
+}
+exports.primraf = primraf;
+/**
+ * Convert a stream to a promise.
+ */
+function streamToPromise(stream) {
+    return new Promise((resolve, reject) => {
+        stream.on('end', _ => resolve());
+        stream.on('error', err => reject(err));
+    });
+}
+exports.streamToPromise = streamToPromise;
+function taskSeries(...tasks) {
+    return async () => {
+        for (let i = 0; i < tasks.length; i++) {
+            await tasks[i]();
+        }
+    };
+}
+exports.taskSeries = taskSeries;
 function getVersion(root) {
     let version = process.env['BUILD_SOURCEVERSION'];
     if (!version || !/^[0-9a-f]{40}$/i.test(version)) {
diff --git a/build/lib/util.ts b/build/lib/util.ts
index 4617cc83f2f04..918c2295b3b1b 100644
--- a/build/lib/util.ts
+++ b/build/lib/util.ts
@@ -237,6 +237,40 @@ export function rimraf(dir: string): (cb: any) => void {
 	return cb => retry(cb);
 }
 
+/**
+ * Like rimraf (with 5 retries), but with a promise instead of a callback.
+ */
+export function primraf(dir: string): Promise<void> {
+	const fn = rimraf(dir);
+	return new Promise((resolve, reject) => {
+		fn((err: any) => {
+			if (err) {
+				return reject(err);
+			}
+			resolve();
+		});
+	});
+}
+
+/**
+ * Convert a stream to a promise.
+ */
+export function streamToPromise(stream: NodeJS.ReadWriteStream): Promise<void> {
+	return new Promise((resolve, reject) => {
+		stream.on('end', _ => resolve());
+		stream.on('error', err => reject(err));
+	});
+}
+
+export type PromiseTask = () => Promise<void>;
+export function taskSeries(...tasks: PromiseTask[]): () => Promise<void> {
+	return async () => {
+		for (let i = 0; i < tasks.length; i++) {
+			await tasks[i]();
+		}
+	};
+}
+
 export function getVersion(root: string): string | undefined {
 	let version = process.env['BUILD_SOURCEVERSION'];
 
diff --git a/gulpfile.js b/gulpfile.js
index 133717f6c3ae4..882d7f8414747 100644
--- a/gulpfile.js
+++ b/gulpfile.js
@@ -21,7 +21,6 @@ gulp.task('watch-client', ['clean-client'], compilation.watchTask('out', false))
 // Full compile, including nls and inline sources in sourcemaps, for build
 gulp.task('clean-client-build', util.rimraf('out-build'));
 gulp.task('compile-client-build', ['clean-client-build'], compilation.compileTask('src', 'out-build', true));
-gulp.task('watch-client-build', ['clean-client-build'], compilation.watchTask('out-build', true));
 
 // Default
 gulp.task('default', ['compile']);
@@ -32,7 +31,6 @@ gulp.task('watch', [/* 'monaco-typecheck-watch', */ 'watch-client', 'watch-exten
 
 // All Build
 gulp.task('compile-build', ['compile-client-build', 'compile-extensions-build']);
-gulp.task('watch-build', ['watch-client-build', 'watch-extensions-build']);
 
 process.on('unhandledRejection', (reason, p) => {
 	console.log('Unhandled Rejection at: Promise', p, 'reason:', reason);