diff --git a/README.md b/README.md
index 609a9f5..dd582e4 100644
--- a/README.md
+++ b/README.md
@@ -83,6 +83,7 @@ deepForceUpdate(rootInstance);
 * Replaces static getters and setters
 * Replaces unbound static methods
 * Replaces static properties unless they were overwritten by code
+* Merges the initial state of new versions with existing component state
 
 ## Known Limitations
 
diff --git a/package.json b/package.json
index 0a11317..30a5148 100644
--- a/package.json
+++ b/package.json
@@ -66,6 +66,7 @@
     "webpack": "1.4.8"
   },
   "dependencies": {
-    "lodash": "^4.6.1"
+    "lodash": "^4.6.1",
+    "shallowequal": "^0.2.2"
   }
 }
diff --git a/src/createClassProxy.js b/src/createClassProxy.js
index b30f804..6094a39 100644
--- a/src/createClassProxy.js
+++ b/src/createClassProxy.js
@@ -2,6 +2,7 @@ import find from 'lodash/find';
 import createPrototypeProxy from './createPrototypeProxy';
 import bindAutoBindMethods from './bindAutoBindMethods';
 import deleteUnknownAutoBindMethods from './deleteUnknownAutoBindMethods';
+import mergeState from './mergeState';
 import supportsProtoAssignment from './supportsProtoAssignment';
 
 const RESERVED_STATICS = [
@@ -173,6 +174,10 @@ function proxyClass(InitialComponent) {
       // We might have added new methods that need to be auto-bound
       mountedInstances.forEach(bindAutoBindMethods);
       mountedInstances.forEach(deleteUnknownAutoBindMethods);
+
+      // Merge the initial state of the next component with
+      // the initial state of the current component
+      mountedInstances.forEach(instance => mergeState(instance, CurrentComponent));
     }
   };
 
diff --git a/src/mergeState.js b/src/mergeState.js
new file mode 100644
index 0000000..74c194d
--- /dev/null
+++ b/src/mergeState.js
@@ -0,0 +1,21 @@
+import assign from 'lodash/assign';
+import React, { Component } from 'react';
+import shallowEqual from 'shallowequal';
+
+export default function mergeState(component, NextComponent) {
+  if (component instanceof React.Component) {
+    // Modern components
+    const nextComponentInstance = new NextComponent(component.props);
+    const mergedState = assign({}, nextComponentInstance.state, component.state);
+    if (!shallowEqual(component.state || {}, mergedState)) {
+      component.setState(mergedState);
+    }
+  } else if (component.getInitialState) {
+    // Classic components
+    const mergedState = assign({}, component.getInitialState(), component.state);
+    if (!shallowEqual(component.state || {}, mergedState)) {
+      component.setState(mergedState);
+    }
+  }
+}
+
diff --git a/test/merge-state.js b/test/merge-state.js
new file mode 100644
index 0000000..1606dca
--- /dev/null
+++ b/test/merge-state.js
@@ -0,0 +1,150 @@
+import React, { Component } from 'react';
+import createShallowRenderer from './helpers/createShallowRenderer';
+import expect from 'expect';
+import createProxy from '../src';
+
+const fixtures = {
+  modern: {
+    VersionA: class VersionA extends React.Component {
+      constructor(props) {
+        super(props);
+      }
+
+      render() {
+        return <div>VersionA</div>;
+      }
+    },
+
+    VersionB: class VersionB extends React.Component {
+      constructor(props) {
+        super(props);
+
+        this.state = {
+          counter: 1,
+        };
+      }
+
+      render() {
+        return <div>VersionB: {this.state.counter}</div>;
+      }
+    },
+
+    VersionC: class VersionC extends React.Component {
+      constructor(props) {
+        super(props);
+        this.state = {
+          counter: 1,
+          secondCounter: 1,
+        };
+      }
+
+      render() {
+        return <div>VersionC: {this.state.counter}{this.state.secondCounter}</div>;
+      }
+    },
+
+    PropsDependent: class PropsDependent extends React.Component {
+      constructor(props) {
+        super(props);
+        
+        this.state = { counter: props.defaultCounter };
+      }
+
+      render() {
+        return <div>{this.state.counter}</div>;
+      }
+    },
+  },
+
+  classic: {
+    ClassicA: React.createClass({
+      render() {
+        return <div>ClassicA</div>;
+      }
+    }),
+
+    ClassicB: React.createClass({
+      getInitialState() {
+        return { counter: 1 };
+      },
+
+      render() {
+        return <div>ClassicB: {this.state.counter}</div>;
+      }
+    }),
+  },
+}
+
+describe('merging state', () => {
+  let renderer;
+  beforeEach(() => {
+    renderer = createShallowRenderer();
+  });
+
+  describe('modern', () => {
+    it('should merge initial state', () => {
+      const { VersionA, VersionB } = fixtures.modern;
+      const proxy = createProxy(VersionA);
+      const Proxy = proxy.get();
+      proxy.update(VersionB);
+      renderer.render(<Proxy/>);
+      expect(renderer.getRenderOutput().props.children).toEqual(['VersionB: ', 1]);
+    });
+
+    it('initializes state based on props', () => {
+      const { VersionA, PropsDependent } = fixtures.modern;
+      const proxy = createProxy(VersionA);
+      const Proxy = proxy.get();
+      renderer.render(<Proxy defaultCounter={3}/>);
+      proxy.update(PropsDependent);
+      renderer.render(<Proxy/>);
+      expect(renderer.getRenderOutput().props.children).toEqual(3);
+    });
+
+    it('does not overwrite existing state', () => {
+      const { VersionA, VersionB } = fixtures.modern;
+      const proxy = createProxy(VersionA);
+      const Proxy = proxy.get();
+      const instance = renderer.render(<Proxy/>);
+      instance.setState({counter: 5});
+      proxy.update(VersionB);
+      renderer.render(<Proxy/>);
+      expect(renderer.getRenderOutput().props.children).toEqual(['VersionB: ', 5]);
+    });
+
+    it('supports multiple updates', () => {
+      const { VersionA, VersionB, VersionC } = fixtures.modern;
+      const proxy = createProxy(VersionA);
+      const Proxy = proxy.get();
+      const instance = renderer.render(<Proxy/>);
+      proxy.update(VersionB);
+      renderer.render(<Proxy/>);
+      proxy.update(VersionC);
+      renderer.render(<Proxy/>);
+      expect(renderer.getRenderOutput().props.children).toEqual(['VersionC: ', 1, 1]);
+    });
+  });
+
+  describe('classic', () => {
+    it('should merge initial state', () => {
+      const { ClassicA, ClassicB } = fixtures.classic;
+      const proxy = createProxy(ClassicA);
+      const Proxy = proxy.get();
+      proxy.update(ClassicB);
+      renderer.render(<Proxy/>);
+      expect(renderer.getRenderOutput().props.children).toEqual(['ClassicB: ', 1]);
+    });
+
+    it('does not overwrite existing state', () => {
+      const { ClassicA, ClassicB } = fixtures.classic;
+      const proxy = createProxy(ClassicA);
+      const Proxy = proxy.get();
+      const instance = renderer.render(<Proxy/>);
+      instance.setState({counter: 5});
+      proxy.update(ClassicB);
+      renderer.render(<Proxy/>);
+      expect(renderer.getRenderOutput().props.children).toEqual(['ClassicB: ', 5]);
+    });
+  });
+});
+