diff --git a/package.json b/package.json
index d208a2f9d..e2e91d181 100644
--- a/package.json
+++ b/package.json
@@ -47,6 +47,7 @@
   "license": "MIT",
   "dependencies": {
     "cheerio": "^0.19.0",
+    "object.assign": "^4.0.3",
     "sinon": "^1.15.4",
     "underscore": "^1.8.3"
   },
diff --git a/src/ReactWrapperComponent.jsx b/src/ReactWrapperComponent.jsx
index 57018316e..698477a72 100644
--- a/src/ReactWrapperComponent.jsx
+++ b/src/ReactWrapperComponent.jsx
@@ -1,4 +1,5 @@
 import React, { PropTypes } from 'react';
+import objectAssign from 'object.assign';
 
 /**
  * This is a utility component to wrap around the nodes we are
@@ -30,7 +31,8 @@ export default function createWrapperComponent(node, options = {}) {
       };
     },
 
-    setChildProps(props) {
+    setChildProps(newProps) {
+      const props = objectAssign({}, this.state.props, newProps);
       return new Promise(resolve => this.setState({ props }, resolve));
     },
 
diff --git a/src/__tests__/ReactWrapper-spec.js b/src/__tests__/ReactWrapper-spec.js
index 40dff38c7..6f6774fac 100644
--- a/src/__tests__/ReactWrapper-spec.js
+++ b/src/__tests__/ReactWrapper-spec.js
@@ -259,6 +259,25 @@ describeWithDOM('mount', () => {
       expect(spy.calledWith(nextProps)).to.equal(true);
     });
 
+    it('should merge newProps with oldProps', () => {
+      class Foo extends React.Component {
+        render() {
+          return (
+            <div {...this.props} />
+          );
+        }
+      }
+
+      const wrapper = mount(<Foo a="a" b="b" />);
+      expect(wrapper.props().a).to.equal('a');
+      expect(wrapper.props().b).to.equal('b');
+
+      wrapper.setProps({ b: 'c', d: 'e' });
+      expect(wrapper.props().a).to.equal('a');
+      expect(wrapper.props().b).to.equal('c');
+      expect(wrapper.props().d).to.equal('e');
+    });
+
   });
 
   describe('.setContext(newContext)', () => {
diff --git a/src/__tests__/ShallowWrapper-spec.js b/src/__tests__/ShallowWrapper-spec.js
index b547ad3db..bc1837aa0 100644
--- a/src/__tests__/ShallowWrapper-spec.js
+++ b/src/__tests__/ShallowWrapper-spec.js
@@ -273,6 +273,25 @@ describe('shallow', () => {
       expect(spy.calledWith(nextProps)).to.equal(true);
     });
 
+    it('should merge newProps with oldProps', () => {
+      class Foo extends React.Component {
+        render() {
+          return (
+            <div {...this.props} />
+          );
+        }
+      }
+
+      const wrapper = shallow(<Foo a="a" b="b" />);
+      expect(wrapper.props().a).to.equal('a');
+      expect(wrapper.props().b).to.equal('b');
+
+      wrapper.setProps({ b: 'c', d: 'e' });
+      expect(wrapper.props().a).to.equal('a');
+      expect(wrapper.props().b).to.equal('c');
+      expect(wrapper.props().d).to.equal('e');
+    });
+
   });
 
   describe('.setContext(newContext)', () => {