diff --git a/src/vs/workbench/services/preferences/common/preferencesValidation.ts b/src/vs/workbench/services/preferences/common/preferencesValidation.ts
index 5c911813f79..9eb757d502c 100644
--- a/src/vs/workbench/services/preferences/common/preferencesValidation.ts
+++ b/src/vs/workbench/services/preferences/common/preferencesValidation.ts
@@ -47,6 +47,10 @@ export function createValidator(prop: IConfigurationPropertySchema): (value: any
 			}
 		}
 
+		if (prop.type === 'boolean' && value !== true && value !== false) {
+			errors.push(nls.localize('validations.booleanIncorrectType', 'Incorrect type. Expected "boolean".'));
+		}
+
 		if (isNumeric) {
 			if (isNullOrEmpty(value) || isNaN(+value)) {
 				errors.push(nls.localize('validations.expectedNumeric', "Value must be a number."));
@@ -57,7 +61,7 @@ export function createValidator(prop: IConfigurationPropertySchema): (value: any
 
 		if (prop.type === 'string') {
 			if (!isString(value)) {
-				errors.push(nls.localize('validations.incorrectType', 'Incorrect type. Expected "string".'));
+				errors.push(nls.localize('validations.stringIncorrectType', 'Incorrect type. Expected "string".'));
 			} else {
 				errors.push(...stringValidations.filter(validator => !validator.isValid(value)).map(validator => validator.message));
 			}
diff --git a/src/vs/workbench/services/preferences/test/common/preferencesValidation.test.ts b/src/vs/workbench/services/preferences/test/common/preferencesValidation.test.ts
index bbb8419aa75..0ee46bad8e7 100644
--- a/src/vs/workbench/services/preferences/test/common/preferencesValidation.test.ts
+++ b/src/vs/workbench/services/preferences/test/common/preferencesValidation.test.ts
@@ -267,6 +267,16 @@ suite('Preferences Validation', () => {
 			pattern.rejects({ '#ab': 99999 });
 			pattern.accepts({});
 		}
+		{
+			const pattern = new Tester({ type: 'object', properties: { 'hello': { type: 'string' } }, additionalProperties: { type: 'boolean' } });
+			pattern.accepts({ 'hello': 'world' });
+			pattern.accepts({ 'hello': 'world', 'bye': false });
+			pattern.rejects({ 'hello': 'world', 'bye': 'false' });
+			pattern.rejects({ 'hello': 'world', 'bye': 1 });
+			pattern.rejects({ 'hello': 'world', 'bye': 'world' });
+			pattern.accepts({ 'hello': 'test' });
+			pattern.accepts({});
+		}
 	});
 
 	test('patterns work', () => {