diff --git a/lib/connectors/memory.js b/lib/connectors/memory.js
index 549bf6f2..7c337d43 100644
--- a/lib/connectors/memory.js
+++ b/lib/connectors/memory.js
@@ -54,6 +54,11 @@ Memory.prototype.loadFromFile = function(callback) {
           data = JSON.parse(data.toString());
           self.ids = data.ids || {};
           self.cache = data.models || {};
+        } else {
+          if(!self.cache) {
+            self.ids = {};
+            self.cache = {};
+          }
         }
         callback && callback();
       }
@@ -80,13 +85,16 @@ Memory.prototype.saveToFile = function (result, callback) {
         }, null, '  ');
 
         fs.writeFile(self.settings.file, data, function (err) {
-          cb(err, result);
-          task && task(err, result);
+          cb(err);
+          task.callback && task.callback(err, task.data);
         });
       }, 1);
     }
     // Enqueue the write
-    self.writeQueue.push(callback);
+    self.writeQueue.push({
+      data: result,
+      callback: callback
+    });
   } else {
     process.nextTick(function () {
       callback && callback(null, result);
@@ -97,8 +105,10 @@ Memory.prototype.saveToFile = function (result, callback) {
 Memory.prototype.define = function defineModel(definition) {
   this.constructor.super_.prototype.define.apply(this, [].slice.call(arguments));
   var m = definition.model.modelName;
-  this.cache[m] = {};
-  this.ids[m] = 1;
+  if(!this.cache[m]) {
+    this.cache[m] = {};
+    this.ids[m] = 1;
+  }
 };
 
 Memory.prototype.create = function create(model, data, callback) {
@@ -121,6 +131,9 @@ Memory.prototype.create = function create(model, data, callback) {
   var idName = this.idName(model);
   id = (props[idName] && props[idName].type && props[idName].type(id)) || id;
   this.setIdValue(model, data, id);
+  if(!this.cache[model]) {
+    this.cache[model] = {};
+  }
   this.cache[model][id] = JSON.stringify(data);
   this.saveToFile(id, callback);
 };
diff --git a/test/memory.test.js b/test/memory.test.js
index dcd8a163..4c613270 100644
--- a/test/memory.test.js
+++ b/test/memory.test.js
@@ -40,10 +40,10 @@ describe('Memory connector', function () {
     });
 
     var count = 0;
-    var id = 1;
+    var ids = [];
     async.eachSeries(['John1', 'John2', 'John3'], function (item, cb) {
       User.create({name: item}, function (err, result) {
-        id = result.id;
+        ids.push(result.id);
         count++;
         readModels(function (err, json) {
           assert.equal(Object.keys(json.models.User).length, count);
@@ -52,10 +52,17 @@ describe('Memory connector', function () {
       });
     }, function (err, results) {
       // Now try to delete one
-      User.deleteById(id, function (err) {
+      User.deleteById(ids[0], function (err) {
         readModels(function (err, json) {
           assert.equal(Object.keys(json.models.User).length, 2);
-          done();
+          User.upsert({id: ids[1], name: 'John'}, function(err, result) {
+            readModels(function (err, json) {
+              assert.equal(Object.keys(json.models.User).length, 2);
+              var user = JSON.parse(json.models.User[ids[1]]);
+              assert.equal(user.name, 'John');
+              done();
+            });
+          });
         });
       });
     });