diff --git a/types/hapi__joi/hapi__joi-tests.ts b/types/hapi__joi/hapi__joi-tests.ts
index c7535d3c9f..bec6360f5c 100644
--- a/types/hapi__joi/hapi__joi-tests.ts
+++ b/types/hapi__joi/hapi__joi-tests.ts
@@ -944,6 +944,9 @@ schema = Joi.link(str);
         value = schema.validate(value).value;
 
         result = schema.validate(value);
+        if (result.error) {
+            throw Error('error should not be set');
+        }
         result = schema.validate(value, validOpts);
         asyncResult = schema.validateAsync(value);
         asyncResult = schema.validateAsync(value, validOpts);
@@ -952,6 +955,12 @@ schema = Joi.link(str);
             .then(val => JSON.stringify(val, null, 2))
             .then(val => { throw new Error('one error'); })
             .catch(e => { });
+
+        const falsyValue = { username: 'example' };
+        result = schema.validate(falsyValue);
+        if (!result.error) {
+            throw Error('error should be set');
+        }
     }
 }
 
diff --git a/types/hapi__joi/index.d.ts b/types/hapi__joi/index.d.ts
index 6444ce5b6b..30b0818c22 100644
--- a/types/hapi__joi/index.d.ts
+++ b/types/hapi__joi/index.d.ts
@@ -20,6 +20,7 @@
 //                 Anand Chowdhary <https://github.com/AnandChowdhary>
 //                 Miro Yovchev <https://github.com/myovchev>
 //                 David Recuenco <https://github.com/RecuencoJones>
+//                 Frederic Reisenhauer <https://github.com/freisenhauer>
 //                 Stefan-Gabriel Muscalu <https://github.com/legraphista>
 // Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
 // TypeScript Version: 2.8
@@ -616,9 +617,9 @@ declare namespace Joi {
     type ValidationErrorFunction = (errors: ValidationErrorItem[]) => string | ValidationErrorItem | Error;
 
     interface ValidationResult<T = any> {
-        error: ValidationError;
-        errors: ValidationError;
-        warning: ValidationError;
+        error?: ValidationError;
+        errors?: ValidationError;
+        warning?: ValidationError;
         value: T;
     }