Hi @oliviertassinari, I have a couple of questions that can help me get an idea of what's happening:

• Can you verify that this.context is undefined and not this.context.muiTheme?
• Do you receive an warning with the following message: Warning: owner-based and parent-based contexts differ...?
• Also can you specify what components are experiencing this error?

One thing we've noticed is having multiple versions of react in your node_modules causes muiTheme to be undefined. Also you are right that we should be using isRequired. We simply glossed over it during development. However, I am not sure if this will solve your problem, but it's worth a try.

• I have a warning like Warning: owner-based and parent-based ...
• I have noticed this problem on the component Paper and Dialog-Window so far.

Oh, indeed, I have two versions of React. I will try with only one.

Using isRequired doesn't solve my problem but would have saved me a lot of time, figuring out the origin of the problem.

I confirm, I solved the problem by using only one version of React.

thanks @mmrtnz

For other people looking for a solution: with webpack you can force all libraries to use the same version of React by setting up an alias. See this blog: http://www.justincarmony.com/blog/2015/04/02/webpack-react-multiple-versions-issues/

Add this to your webpack.config.js for a quick fix:

module.exports = {
    // ... other settings ...

    resolve: {
        // ...other resolve settings ...
        alias: {
            "react": __dirname + '/node_modules/react',
            "react/addons": __dirname + '/node_modules/react/addons',
        }
    }

    // ... other settings ...
}

@oliviertassinari How do you set only one React version? Now I'm using webpack and react version is 0.1.3.3.
let React = require('react');
let mui = require('material-ui');
I use these to import them, and the build file has two React.version.
thanks

@xushao0305 I had one react directory at the first level of node_modules and a second one at the level of material-ui. I removed the second one.

@oliviertassinari Fine! It works after I remove the React directory of material-ui. Thanks.
But in production env.We use npm install to get material-ui, and it take the second react, Is there some way to remove it automatic?

The react folder appears inside material-ui if you run npm install in the material-ui directory.
npm do a flat dependancy resolution. This means that after running npm install at the root of your project, you should have only one react folder.

@oliviertassinari OK. thanks olivier