diff --git a/lib/commands/env/add.ts b/lib/commands/env/add.ts
index 318717da..479e03c4 100644
--- a/lib/commands/env/add.ts
+++ b/lib/commands/env/add.ts
@@ -90,6 +90,8 @@ export default class EnvAddCmd extends Command {
 		}),
 	};
 
+	// Required for supporting empty string ('') `value` args.
+	public static strict = false;
 	public static usage = 'env add <name> [value]';
 
 	public static flags = {
diff --git a/lib/commands/tag/set.ts b/lib/commands/tag/set.ts
index db2549ed..d77e4190 100644
--- a/lib/commands/tag/set.ts
+++ b/lib/commands/tag/set.ts
@@ -56,6 +56,8 @@ export default class TagSetCmd extends Command {
 		}),
 	};
 
+	// Required for supporting empty string ('') `value` args.
+	public static strict = false;
 	public static usage = 'tag set <tagKey> [value]';
 
 	public static flags = {
diff --git a/tests/commands/env/add.spec.ts b/tests/commands/env/add.spec.ts
index 7412f7a5..b8d3d095 100644
--- a/tests/commands/env/add.spec.ts
+++ b/tests/commands/env/add.spec.ts
@@ -23,6 +23,8 @@ import { runCommand } from '../../helpers';
 describe('balena env add', function () {
 	let api: BalenaAPIMock;
 
+	const fullUUID = 'f63fd7d7812c34c4c14ae023fdff05f5';
+
 	beforeEach(() => {
 		api = new BalenaAPIMock();
 		api.expectGetWhoAmI({ optional: true, persist: true });
@@ -35,7 +37,6 @@ describe('balena env add', function () {
 	});
 
 	it('should successfully add an environment variable', async () => {
-		const fullUUID = 'f63fd7d7812c34c4c14ae023fdff05f5';
 		api.expectGetDevice({ fullUUID });
 		api.expectGetConfigVars();
 		api.scope
@@ -47,4 +48,58 @@ describe('balena env add', function () {
 		expect(out.join('')).to.equal('');
 		expect(err.join('')).to.equal('');
 	});
+
+	it('should reject adding an environment variable w/o specifying a value when the process environment does not have an env var with the same name defined', async () => {
+		// make sure that that there is no such env var defined atm
+		delete process.env.TEST_ENV_VAR_ADD_NO_VALUE_REJECTED;
+
+		const { out, err } = await runCommand(
+			`env add TEST_ENV_VAR_ADD_NO_VALUE_REJECTED -d ${fullUUID}`,
+		);
+
+		expect(out.join('')).to.equal('');
+		// Depending the context that the test was running , this was emiting either 1 or 2 '\n'
+		expect(err.join('')).to.be.oneOf([
+			'Value not found for environment variable: TEST_ENV_VAR_ADD_NO_VALUE_REJECTED\n',
+			'Value not found for environment variable: TEST_ENV_VAR_ADD_NO_VALUE_REJECTED\n\n',
+		]);
+	});
+
+	it('should successfully add an environment variable w/o specifying a value when the process environment has an env var with the same name defined', async () => {
+		api.expectGetDevice({ fullUUID });
+		api.expectGetConfigVars();
+		api.scope
+			.post(/^\/v\d+\/device_environment_variable($|\?)/)
+			.reply(200, 'OK');
+
+		process.env.TEST_ENV_VAR_ADD_NO_VALUE = '4';
+
+		const { out, err } = await runCommand(
+			`env add TEST_ENV_VAR_ADD_NO_VALUE -d ${fullUUID}`,
+		);
+
+		delete process.env.TEST_ENV_VAR_ADD_NO_VALUE;
+
+		expect(out.join('')).to.equal('');
+		expect(err.join('')).to.be.oneOf([
+			' ›   Warning: Using TEST_ENV_VAR_ADD_NO_VALUE=4 from CLI process environment\n',
+			// emitted when running on the windows instance
+			' »   Warning: Using TEST_ENV_VAR_ADD_NO_VALUE=4 from CLI process environment\n',
+		]);
+	});
+
+	it('should successfully add an environment variable w/ empty string as a value', async () => {
+		api.expectGetDevice({ fullUUID });
+		api.expectGetConfigVars();
+		api.scope
+			.post(/^\/v\d+\/device_environment_variable($|\?)/)
+			.reply(200, 'OK');
+
+		const { out, err } = await runCommand(
+			`env add TEST_EMPTY_STRING '' -d ${fullUUID}`,
+		);
+
+		expect(out.join('')).to.equal('');
+		expect(err.join('')).to.equal('');
+	});
 });
diff --git a/tests/commands/tag/set.spec.ts b/tests/commands/tag/set.spec.ts
new file mode 100644
index 00000000..0ed18fde
--- /dev/null
+++ b/tests/commands/tag/set.spec.ts
@@ -0,0 +1,72 @@
+/**
+ * @license
+ * Copyright 2019-2020 Balena Ltd.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { expect } from 'chai';
+
+import { BalenaAPIMock } from '../../nock/balena-api-mock';
+import { runCommand } from '../../helpers';
+
+describe('balena tag set', function () {
+	let api: BalenaAPIMock;
+
+	const fullUUID = 'f63fd7d7812c34c4c14ae023fdff05f5';
+
+	beforeEach(() => {
+		api = new BalenaAPIMock();
+		api.expectGetWhoAmI({ optional: true, persist: true });
+		api.expectGetMixpanel({ optional: true });
+	});
+
+	afterEach(() => {
+		// Check all expected api calls have been made and clean up.
+		api.done();
+	});
+
+	it('should successfully set a tag', async () => {
+		api.expectGetDevice({ fullUUID });
+		api.scope.post(/^\/v\d+\/device_tag($|\?)/).reply(200, 'OK');
+
+		const { out, err } = await runCommand(`tag set TEST 1 -d ${fullUUID}`);
+
+		expect(out.join('')).to.equal('');
+		expect(err.join('')).to.equal('');
+	});
+
+	it('should successfully set a tag w/o specifying a value', async () => {
+		api.expectGetDevice({ fullUUID });
+		api.scope.post(/^\/v\d+\/device_tag($|\?)/).reply(200, 'OK');
+
+		const { out, err } = await runCommand(
+			`tag set TEST_NO_VALUE -d ${fullUUID}`,
+		);
+
+		expect(out.join('')).to.equal('');
+		expect(err.join('')).to.equal('');
+	});
+
+	it('should successfully set a tag w/ empty string as a value', async () => {
+		api.expectGetDevice({ fullUUID });
+		api.scope.post(/^\/v\d+\/device_tag($|\?)/).reply(200, 'OK');
+
+		const { out, err } = await runCommand(
+			`tag set TEST_EMPTY_STRING '' -d ${fullUUID}`,
+		);
+
+		expect(out.join('')).to.equal('');
+		expect(err.join('')).to.equal('');
+	});
+});