diff --git a/helpers/legacyStore.js b/helpers/legacyStore.js
index a7f3575..142f60e 100644
--- a/helpers/legacyStore.js
+++ b/helpers/legacyStore.js
@@ -6,13 +6,31 @@ var assign = require("can-util/js/assign/assign");
 
 module.exports = function (count, make, filter) {
 	/*jshint eqeqeq:false */
-	var getUniqueId = (function () {
+	var nextUniqueId = (function () {
 		var i = 0;
 		return function () {
 			return i++;
 		}
 	})();
 
+	// Check to see if an existing item has the ID we want to assign
+	var isIdUnique = function (items, id) {
+		for (var key in items) {
+			if (items[key].id === id) {
+				return false;
+			}
+		}
+		return true;
+	}
+
+	var getUniqueId = function (items) {
+		var id = nextUniqueId();
+		while (!isIdUnique(items, id)) {
+			id = nextUniqueId();
+		}
+		return id;
+	}
+
 	var items,
 		findOne = function (id) {
 			for (var i = 0; i < items.length; i++) {
@@ -47,7 +65,7 @@ module.exports = function (count, make, filter) {
 				var item = make(i, items);
 
 				if (!item.id) {
-					item.id = getUniqueId();
+					item.id = getUniqueId(items);
 				}
 				items.push(item);
 			}
@@ -256,7 +274,7 @@ module.exports = function (count, make, filter) {
 			// If an ID wasn't passed into the request, we give the item
 			// a unique ID.
 			if (!item.id) {
-				item.id = getUniqueId();
+				item.id = getUniqueId(items);
 			}
 
 			// Push the new item into the store.
diff --git a/test/fixture_test.js b/test/fixture_test.js
index 3eaa62e..4dc23f4 100644
--- a/test/fixture_test.js
+++ b/test/fixture_test.js
@@ -225,6 +225,57 @@ test('fixture.store fixtures should have unique IDs', function () {
 	});
 });
 
+test('fixture.store should assign unique IDs when fixtures provide IDs', function () {
+	/* NOTE: We are testing whether the unique ID we are assigning to a new
+	         item will account for IDs which the user has provided.
+	*/
+
+	/* NOTE: These integers are used because IDs are created sequentially from 0.
+	         Here, 0 1 and 2 must be skipped because they exist already.
+	         If the implementation is changed this test will need updated.
+	*/
+	var store = fixture.store([
+		{id: 0, name: 'Object 0'},
+		{id: 1, name: 'Object 1'},
+		{id: 2, name: 'Object 2'}
+	]);
+
+	fixture('POST /models', store.createData);
+
+	function then (ajax, callback) {
+		ajax.then(callback, function (error) {
+			ok(false, 'ajax failure: ' + error);
+			start();
+		});
+	}
+
+	var request = $.ajax({
+		url: '/models',
+		dataType: 'json',
+		type: 'post',
+		data: {
+			name: 'My test object'
+		}
+	});
+
+	stop();
+	then(request, function (response) {
+		notEqual(response.id, 0);
+		notEqual(response.id, 1);
+		notEqual(response.id, 2);
+
+		/* NOTE: This check will fail if the underlying implementation changes.
+		         This 3 is tightly coupled to the implementation.
+		         If this is the only breaking assertion, update the provided IDs to
+		         properly test the edge-case and update these assertions.
+		         This check only serves to notify you to update the checks.
+		*/
+		equal(response.id, 3);
+
+		start();
+	});
+});
+
 test('simulating an error', function () {
 
 	fixture('/foo', function (request, response) {