diff --git a/src/validators/common.ts b/src/validators/common.ts
index ecee8b16..80d0d779 100644
--- a/src/validators/common.ts
+++ b/src/validators/common.ts
@@ -70,11 +70,19 @@ export function validateAliasPrimary(value: any): void {
 	}
 }
 
+export function validateAliasDefault(value: any): void {
+	// Property is optional, it only exists for imported entities.
+	if (!(_.isNil(value) || _.isBoolean(value))) {
+		throw new ValidationError('Value has to be a boolean, `null` or `undefined`', 'alias.default', value);
+	}
+}
+
 export function validateAlias(value: any): void {
 	validateAliasName(get(value, 'name'));
 	validateAliasSortName(get(value, 'sortName'));
 	validateAliasLanguage(get(value, 'language'));
 	validateAliasPrimary(get(value, 'primary'));
+	validateAliasDefault(get(value, 'default', null));
 }
 
 export const validateAliases = _.partial(
diff --git a/test/validators/test-alias.js b/test/validators/test-alias.js
index 1bf0e722..674a6296 100644
--- a/test/validators/test-alias.js
+++ b/test/validators/test-alias.js
@@ -25,7 +25,7 @@ import {
 	testValidateStringFunc
 } from './helpers';
 import {
-	validateAlias, validateAliasLanguage, validateAliasName,
+	validateAlias, validateAliasDefault, validateAliasLanguage, validateAliasName,
 	validateAliasPrimary, validateAliasSortName, validateAliases
 } from '../../lib/validators/common';
 import {ValidationError} from '../../lib/validators/base';
@@ -53,11 +53,19 @@ function describeValidateAliasPrimary() {
 	testValidateBooleanFunc(validateAliasPrimary);
 }
 
+function describeValidateAliasDefault() {
+	testValidateBooleanFunc(validateAliasDefault, false);
+}
+
 function describeValidateAlias() {
 	it('should pass a valid Object', () => {
 		expect(() => validateAlias(VALID_ALIAS)).to.not.throw();
 	});
 
+	it('should pass a valid Object with a default flag', () => {
+		expect(() => validateAlias({...VALID_ALIAS, default: true})).to.not.throw();
+	});
+
 	it('should pass a valid Immutable.Map', () => {
 		expect(() => validateAlias(Immutable.fromJS(VALID_ALIAS))).to.not.throw();
 	});
@@ -132,6 +140,7 @@ function tests() {
 	describe('validateAliasLanguage', describeValidateAliasLanguage);
 	describe('validateAlias', describeValidateAlias);
 	describe('validateAliasPrimary', describeValidateAliasPrimary);
+	describe('validateAliasDefault', describeValidateAliasDefault);
 	describe('validateAliases', describeValidateAliases);
 }