From 9f933a0faaada42d0f5bc8db8e53d99ce08f3103 Mon Sep 17 00:00:00 2001
From: Jichao Ouyang <oyanglulu@gmail.com>
Date: Wed, 16 Nov 2016 15:44:49 +0800
Subject: [PATCH] check type first, then name

---
 test/index.js | 2 ++
 union-type.js | 2 +-
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/test/index.js b/test/index.js
index 59d4876..54af483 100644
--- a/test/index.js
+++ b/test/index.js
@@ -121,10 +121,12 @@ describe('union type', function() {
   describe('predicate', function() {
     it('can use predicate to check type', function() {
       var Maybe = Type({Just: [T], Nothing: []});
+      var OtherMaybe = Type({Just: [T]});
       var just1 = Maybe.Just(1)
       assert.equal(Maybe.isJust(just1), true);
       assert.equal(Maybe.isNothing(just1), false);
       assert.equal(Maybe.isNothing(just1), false);
+      assert.equal(OtherMaybe.isJust(just1), false);
     })
   });
   describe('type methods', function() {
diff --git a/union-type.js b/union-type.js
index cd9b7ea..d465e8b 100644
--- a/union-type.js
+++ b/union-type.js
@@ -76,7 +76,7 @@ function constructor(group, name, fields) {
   }
   group[name] = curryN(keys.length, construct);
   group['is' + name] = function(value) {
-    return name === value._name
+    return group.prototype.isPrototypeOf(value) && name === value._name
   }
   if (keys !== undefined) {
     group[name+'Of'] = function(obj) {