4 files changed, 7 insertions, 3 deletions
diff --git a/packages/gitbook-core/package.json b/packages/gitbook-core/package.json
index caf2fe2..1137d32 100644
--- a/packages/gitbook-core/package.json
+++ b/packages/gitbook-core/package.json
@@ -9,6 +9,7 @@
     "react": "^15.3.1",
     "react-dom": "^15.3.1",
     "react-helmet": "^3.1.0",
+    "react-immutable-proptypes": "^2.1.0",
     "react-redux": "^4.4.5",
     "react-safe-html": "^0.3.0",
     "redux": "^3.5.2",
diff --git a/packages/gitbook-core/src/shapes/File.js b/packages/gitbook-core/src/shapes/File.js
index cff2219..6c7df3e 100644
--- a/packages/gitbook-core/src/shapes/File.js
+++ b/packages/gitbook-core/src/shapes/File.js
@@ -2,12 +2,13 @@ const React  = require('react');
 const {
     oneOf,
     string,
+    instanceOf,
     shape
 } = React.PropTypes;
 
 
 module.exports = shape({
-    mtime: string.isRequired,
+    mtime: instanceOf(Date).isRequired,
     path:  string.isRequired,
     type:  oneOf(['markdown', 'asciidoc']).isRequired
 });
diff --git a/packages/gitbook-core/src/shapes/index.js b/packages/gitbook-core/src/shapes/index.js
index 149b5a7..68966ba 100644
--- a/packages/gitbook-core/src/shapes/index.js
+++ b/packages/gitbook-core/src/shapes/index.js
@@ -1,5 +1,7 @@
+const ImmutablePropTypes = require('react-immutable-proptypes');
 
 module.exports = {
+    ...ImmutablePropTypes,
     Page:           require('./Page'),
     File:           require('./File'),
     Summary:        require('./Summary'),
diff --git a/packages/gitbook-plugin-theme-default/src/Summary.js b/packages/gitbook-plugin-theme-default/src/Summary.js
index 13b74c1..e95b4b4 100644
--- a/packages/gitbook-plugin-theme-default/src/Summary.js
+++ b/packages/gitbook-plugin-theme-default/src/Summary.js
@@ -21,7 +21,7 @@ const SummaryArticle = React.createClass({
 
 const SummaryArticles = React.createClass({
     propTypes: {
-        articles: React.PropTypes.arrayOf(GitBook.Shapes.SummaryArticle)
+        articles: GitBook.Shapes.listOf(GitBook.Shapes.SummaryArticle)
     },
 
     render() {
@@ -59,7 +59,7 @@ const SummaryPart = React.createClass({
 
 const SummaryParts = React.createClass({
     propTypes: {
-        parts: React.PropTypes.arrayOf(GitBook.Shapes.SummaryPart)
+        parts: GitBook.Shapes.listOf(GitBook.Shapes.SummaryPart)
     },
 
     render() {