diff --git a/lib/actions/build.coffee b/lib/actions/build.coffee
deleted file mode 100644
index f34f82b7..00000000
--- a/lib/actions/build.coffee
+++ /dev/null
@@ -1,186 +0,0 @@
-###*
-# @license
-# Copyright 2016-2020 Balena Ltd.
-#
-# Licensed under the Apache License, Version 2.0 (the "License");
-# you may not use this file except in compliance with the License.
-# You may obtain a copy of the License at
-#
-#    http://www.apache.org/licenses/LICENSE-2.0
-#
-# Unless required by applicable law or agreed to in writing, software
-# distributed under the License is distributed on an "AS IS" BASIS,
-# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-# See the License for the specific language governing permissions and
-# limitations under the License.
-###
-
-# Imported here because it's needed for the setup
-# of this action
-Promise = require('bluebird')
-dockerUtils = require('../utils/docker')
-compose = require('../utils/compose')
-{ registrySecretsHelp } = require('../utils/messages')
-{ getBalenaSdk } = require('../utils/lazy')
-
-###
-Opts must be an object with the following keys:
-
-	app: the app this build is for (optional)
-	arch: the architecture to build for
-	deviceType: the device type to build for
-	buildEmulated
-	buildOpts: arguments to forward to docker build command
-###
-buildProject = (docker, logger, composeOpts, opts) ->
-	{ loadProject } = require('../utils/compose_ts')
-	Promise.resolve(loadProject(logger, composeOpts))
-	.then (project) ->
-		appType = opts.app?.application_type?[0]
-		if appType? and project.descriptors.length > 1 and not appType.supports_multicontainer
-			logger.logWarn(
-				'Target application does not support multiple containers.\n' +
-				'Continuing with build, but you will not be able to deploy.'
-			)
-
-		compose.buildProject(
-			docker
-			logger
-			project.path
-			project.name
-			project.composition
-			opts.arch
-			opts.deviceType
-			opts.buildEmulated
-			opts.buildOpts
-			composeOpts.inlineLogs
-			opts.convertEol
-			composeOpts.dockerfilePath
-		)
-	.then ->
-		logger.outputDeferredMessages()
-		logger.logSuccess('Build succeeded!')
-	.tapCatch (e) ->
-		logger.logError('Build failed')
-
-module.exports =
-	signature: 'build [source]'
-	description: 'Build a single image or a multicontainer project locally'
-	primary: true
-	help: """
-		Use this command to build an image or a complete multicontainer project with
-		the provided docker daemon in your development machine or balena device.
-		(See also the `balena push` command for the option of building images in the
-		balenaCloud build servers.)
-
-		You must provide either an application or a device-type/architecture pair to use
-		the balena Dockerfile pre-processor (e.g. Dockerfile.template -> Dockerfile).
-
-		This command will look into the given source directory (or the current working
-		directory if one isn't specified) for a docker-compose.yml file, and if found,
-		each service defined in the compose file will be built. If a compose file isn't
-		found, it will look for a Dockerfile[.template] file (or alternative Dockerfile
-		specified with the `--dockerfile` option), and if no dockerfile is found, it
-		will try to generate one.
-
-		#{registrySecretsHelp}
-
-		Examples:
-
-			$ balena build
-			$ balena build ./source/
-			$ balena build --deviceType raspberrypi3 --arch armv7hf --emulated
-			$ balena build --application MyApp ./source/
-			$ balena build --docker /var/run/docker.sock   # Linux, Mac
-			$ balena build --docker //./pipe/docker_engine # Windows
-			$ balena build --dockerHost my.docker.host --dockerPort 2376 --ca ca.pem --key key.pem --cert cert.pem
-	"""
-	options: dockerUtils.appendOptions compose.appendOptions [
-		{
-			signature: 'arch'
-			parameter: 'arch'
-			description: 'The architecture to build for'
-			alias: 'A'
-		},
-		{
-			signature: 'deviceType'
-			parameter: 'deviceType'
-			description: 'The type of device this build is for'
-			alias: 'd'
-		},
-		{
-			signature: 'application'
-			parameter: 'application'
-			description: 'The target balena application this build is for'
-			alias: 'a'
-		},
-	]
-	action: (params, options) ->
-		# compositions with many services trigger misleading warnings
-		require('events').defaultMaxListeners = 1000
-
-		sdk = getBalenaSdk()
-		{ ExpectedError } = require('../errors')
-		{ checkLoggedIn } = require('../utils/patterns')
-		{ validateProjectDirectory } = require('../utils/compose_ts')
-		helpers = require('../utils/helpers')
-		Logger = require('../utils/logger')
-
-		logger = Logger.getLogger()
-		logger.logDebug('Parsing input...')
-
-		# `build` accepts `[source]` as a parameter, but compose expects it
-		# as an option. swap them here
-		options.source ?= params.source
-		delete params.source
-
-		options.convertEol = options['convert-eol'] || false
-		delete options['convert-eol']
-
-		{ application, arch, deviceType } = options
-
-		Promise.try ->
-			if (not (arch? and deviceType?) and not application?) or (application? and (arch? or deviceType?))
-				throw new ExpectedError('You must specify either an application or an arch/deviceType pair to build for')
-			if (application)
-				checkLoggedIn()
-		.then ->
-			validateProjectDirectory(sdk, {
-				dockerfilePath: options.dockerfile,
-				noParentCheck: options['noparent-check'] || false,
-				projectPath: options.source || '.',
-				registrySecretsPath: options['registry-secrets'],
-			})
-		.then ({ dockerfilePath, registrySecrets }) ->
-			options.dockerfile = dockerfilePath
-			options['registry-secrets'] = registrySecrets
-
-			if arch? and deviceType?
-				[ undefined, arch, deviceType ]
-			else
-				Promise.join(
-					helpers.getApplication(application)
-					helpers.getArchAndDeviceType(application)
-					(app, { arch, device_type }) ->
-						app.arch = arch
-						app.device_type = device_type
-						return app
-				)
-				.then (app) ->
-					[ app, app.arch, app.device_type ]
-
-		.then ([ app, arch, deviceType ]) ->
-			Promise.join(
-				dockerUtils.getDocker(options)
-				dockerUtils.generateBuildOpts(options)
-				compose.generateOpts(options)
-				(docker, buildOpts, composeOpts) ->
-					buildProject(docker, logger, composeOpts, {
-						app
-						arch
-						deviceType
-						buildEmulated: !!options.emulated
-						buildOpts
-						convertEol: options.convertEol
-					})
-			)
diff --git a/lib/actions/build.js b/lib/actions/build.js
new file mode 100644
index 00000000..f2f03b35
--- /dev/null
+++ b/lib/actions/build.js
@@ -0,0 +1,221 @@
+/**
+ * @license
+ * Copyright 2016-2020 Balena Ltd.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+// Imported here because it's needed for the setup
+// of this action
+import * as Promise from 'bluebird';
+
+import * as dockerUtils from '../utils/docker';
+import * as compose from '../utils/compose';
+import { registrySecretsHelp } from '../utils/messages';
+import { getBalenaSdk } from '../utils/lazy';
+
+/*
+Opts must be an object with the following keys:
+
+	app: the app this build is for (optional)
+	arch: the architecture to build for
+	deviceType: the device type to build for
+	buildEmulated
+	buildOpts: arguments to forward to docker build command
+*/
+const buildProject = function(docker, logger, composeOpts, opts) {
+	const { loadProject } = require('../utils/compose_ts');
+	return Promise.resolve(loadProject(logger, composeOpts))
+		.then(function(project) {
+			const appType = opts.app?.application_type?.[0];
+			if (
+				appType != null &&
+				project.descriptors.length > 1 &&
+				!appType.supports_multicontainer
+			) {
+				logger.logWarn(
+					'Target application does not support multiple containers.\n' +
+						'Continuing with build, but you will not be able to deploy.',
+				);
+			}
+
+			return compose.buildProject(
+				docker,
+				logger,
+				project.path,
+				project.name,
+				project.composition,
+				opts.arch,
+				opts.deviceType,
+				opts.buildEmulated,
+				opts.buildOpts,
+				composeOpts.inlineLogs,
+				opts.convertEol,
+				composeOpts.dockerfilePath,
+			);
+		})
+		.then(function() {
+			logger.outputDeferredMessages();
+			logger.logSuccess('Build succeeded!');
+		})
+		.tapCatch(() => {
+			logger.logError('Build failed');
+		});
+};
+
+export const build = {
+	signature: 'build [source]',
+	description: 'Build a single image or a multicontainer project locally',
+	primary: true,
+	help: `\
+Use this command to build an image or a complete multicontainer project with
+the provided docker daemon in your development machine or balena device.
+(See also the \`balena push\` command for the option of building images in the
+balenaCloud build servers.)
+
+You must provide either an application or a device-type/architecture pair to use
+the balena Dockerfile pre-processor (e.g. Dockerfile.template -> Dockerfile).
+
+This command will look into the given source directory (or the current working
+directory if one isn't specified) for a docker-compose.yml file, and if found,
+each service defined in the compose file will be built. If a compose file isn't
+found, it will look for a Dockerfile[.template] file (or alternative Dockerfile
+specified with the \`--dockerfile\` option), and if no dockerfile is found, it
+will try to generate one.
+
+${registrySecretsHelp}
+
+Examples:
+
+	$ balena build
+	$ balena build ./source/
+	$ balena build --deviceType raspberrypi3 --arch armv7hf --emulated
+	$ balena build --application MyApp ./source/
+	$ balena build --docker /var/run/docker.sock   # Linux, Mac
+	$ balena build --docker //./pipe/docker_engine # Windows
+	$ balena build --dockerHost my.docker.host --dockerPort 2376 --ca ca.pem --key key.pem --cert cert.pem\
+`,
+	options: dockerUtils.appendOptions(
+		compose.appendOptions([
+			{
+				signature: 'arch',
+				parameter: 'arch',
+				description: 'The architecture to build for',
+				alias: 'A',
+			},
+			{
+				signature: 'deviceType',
+				parameter: 'deviceType',
+				description: 'The type of device this build is for',
+				alias: 'd',
+			},
+			{
+				signature: 'application',
+				parameter: 'application',
+				description: 'The target balena application this build is for',
+				alias: 'a',
+			},
+		]),
+	),
+	action(params, options) {
+		// compositions with many services trigger misleading warnings
+		// @ts-ignore editing property that isn't typed but does exist
+		require('events').defaultMaxListeners = 1000;
+
+		const sdk = getBalenaSdk();
+		const { ExpectedError } = require('../errors');
+		const { checkLoggedIn } = require('../utils/patterns');
+		const { validateProjectDirectory } = require('../utils/compose_ts');
+		const helpers = require('../utils/helpers');
+		const Logger = require('../utils/logger');
+
+		const logger = Logger.getLogger();
+		logger.logDebug('Parsing input...');
+
+		// `build` accepts `[source]` as a parameter, but compose expects it
+		// as an option. swap them here
+		if (options.source == null) {
+			options.source = params.source;
+		}
+		delete params.source;
+
+		options.convertEol = options['convert-eol'] || false;
+		delete options['convert-eol'];
+
+		const { application, arch, deviceType } = options;
+
+		return Promise.try(function() {
+			if (
+				(application == null && (arch == null || deviceType == null)) ||
+				(application != null && (arch != null || deviceType != null))
+			) {
+				throw new ExpectedError(
+					'You must specify either an application or an arch/deviceType pair to build for',
+				);
+			}
+			if (application) {
+				return checkLoggedIn();
+			}
+		})
+			.then(() =>
+				validateProjectDirectory(sdk, {
+					dockerfilePath: options.dockerfile,
+					noParentCheck: options['noparent-check'] || false,
+					projectPath: options.source || '.',
+					registrySecretsPath: options['registry-secrets'],
+				}),
+			)
+			.then(function({ dockerfilePath, registrySecrets }) {
+				options.dockerfile = dockerfilePath;
+				options['registry-secrets'] = registrySecrets;
+
+				if (arch != null && deviceType != null) {
+					return [undefined, arch, deviceType];
+				} else {
+					return Promise.join(
+						helpers.getApplication(application),
+						helpers.getArchAndDeviceType(application),
+						function(
+							app,
+							{ arch: resolvedArch, device_type: resolvedDeviceType },
+						) {
+							// @ts-ignore extending the app object
+							app.arch = resolvedArch;
+							app.device_type = resolvedDeviceType;
+							return app;
+						},
+					).then(app =>
+						// @ts-ignore using the extended prop
+						[app, app.arch, app.device_type],
+					);
+				}
+			})
+
+			.then(function([app, resolvedArch, resolvedDeviceType]) {
+				return Promise.join(
+					dockerUtils.getDocker(options),
+					dockerUtils.generateBuildOpts(options),
+					compose.generateOpts(options),
+					(docker, buildOpts, composeOpts) =>
+						buildProject(docker, logger, composeOpts, {
+							app,
+							arch: resolvedArch,
+							deviceType: resolvedDeviceType,
+							buildEmulated: !!options.emulated,
+							buildOpts,
+							convertEol: options.convertEol,
+						}),
+				);
+			});
+	},
+};
diff --git a/lib/actions/index.coffee b/lib/actions/index.coffee
index 524c8978..eb7fbb26 100644
--- a/lib/actions/index.coffee
+++ b/lib/actions/index.coffee
@@ -26,7 +26,7 @@ module.exports =
 	os: require('./os')
 	config: require('./config')
 	ssh: require('./ssh')
-	build: require('./build')
+	build: require('./build').build
 	deploy: require('./deploy')
 	util: require('./util')
 	preload: require('./preload').preload