diff --git a/packages/index-model/lib/model.js b/packages/index-model/lib/model.js
index a94b46a4798..9765acdc506 100644
--- a/packages/index-model/lib/model.js
+++ b/packages/index-model/lib/model.js
@@ -47,7 +47,7 @@ var IndexModel = Model.extend({
     ttl: {
       deps: ['extra'],
       fn: function() {
-        return !!this.extra.expireAfterSeconds;
+        return this.extra.expireAfterSeconds > -1;
       }
     },
     hashed: {
diff --git a/packages/index-model/test/index.test.js b/packages/index-model/test/index.test.js
index 45ac2b7d361..b8d71711318 100644
--- a/packages/index-model/test/index.test.js
+++ b/packages/index-model/test/index.test.js
@@ -1,4 +1,5 @@
 var assert = require('assert');
+var IndexModel = require('../');
 var IndexCollection = require('../').Collection;
 var _ = require('lodash');
 
@@ -140,6 +141,32 @@ describe('mongodb-index-model', function() {
       assert.ok('columnstore' in index);
       assert.ok('text' in index);
     });
+
+    it('calculates correct ttl', function() {
+      assert.equal(
+        (new IndexModel(new IndexModel().parse({expireAfterSeconds: 20}))).ttl,
+        true,
+        'its ttl when expireAfterSeconds is 20'
+      );
+
+      assert.equal(
+        (new IndexModel(new IndexModel().parse({expireAfterSeconds: 0}))).ttl,
+        true,
+        'its ttl when expireAfterSeconds is 0'
+      );
+
+      assert.equal(
+        (new IndexModel(new IndexModel().parse({expireAfterSeconds: undefined}))).ttl,
+        false,
+        'its not ttl when expireAfterSeconds is undefined'
+      );
+
+      assert.equal(
+        (new IndexModel(new IndexModel().parse({}))).ttl,
+        false,
+        'its just not ttl'
+      );
+    });
   });
 
   context('IndexField', function() {