diff --git a/src/BootstrapMixin.js b/src/BootstrapMixin.js
index 00eb552f99..f158c58bc8 100644
--- a/src/BootstrapMixin.js
+++ b/src/BootstrapMixin.js
@@ -1,28 +1,28 @@
-import React from 'react';
-import constants from './constants';
+import styleMaps from './styleMaps';
+import CustomPropTypes from './utils/CustomPropTypes';
 
 const BootstrapMixin = {
   propTypes: {
-    bsClass: React.PropTypes.oneOf(Object.keys(constants.CLASSES)),
-    bsStyle: React.PropTypes.oneOf(Object.keys(constants.STYLES)),
-    bsSize: React.PropTypes.oneOf(Object.keys(constants.SIZES))
+    bsClass: CustomPropTypes.keyOf(styleMaps.CLASSES),
+    bsStyle: CustomPropTypes.keyOf(styleMaps.STYLES),
+    bsSize: CustomPropTypes.keyOf(styleMaps.SIZES)
   },
 
   getBsClassSet() {
     let classes = {};
 
-    let bsClass = this.props.bsClass && constants.CLASSES[this.props.bsClass];
+    let bsClass = this.props.bsClass && styleMaps.CLASSES[this.props.bsClass];
     if (bsClass) {
       classes[bsClass] = true;
 
       let prefix = bsClass + '-';
 
-      let bsSize = this.props.bsSize && constants.SIZES[this.props.bsSize];
+      let bsSize = this.props.bsSize && styleMaps.SIZES[this.props.bsSize];
       if (bsSize) {
         classes[prefix + bsSize] = true;
       }
 
-      let bsStyle = this.props.bsStyle && constants.STYLES[this.props.bsStyle];
+      let bsStyle = this.props.bsStyle && styleMaps.STYLES[this.props.bsStyle];
       if (this.props.bsStyle) {
         classes[prefix + bsStyle] = true;
       }
@@ -32,7 +32,7 @@ const BootstrapMixin = {
   },
 
   prefixClass(subClass) {
-    return constants.CLASSES[this.props.bsClass] + '-' + subClass;
+    return styleMaps.CLASSES[this.props.bsClass] + '-' + subClass;
   }
 };
 
diff --git a/src/Col.js b/src/Col.js
index 23ae471ad1..0898e10b2e 100644
--- a/src/Col.js
+++ b/src/Col.js
@@ -1,6 +1,6 @@
 import React from 'react';
 import classNames from 'classnames';
-import constants from './constants';
+import styleMaps from './styleMaps';
 
 const Col = React.createClass({
   propTypes: {
@@ -33,8 +33,8 @@ const Col = React.createClass({
     let ComponentClass = this.props.componentClass;
     let classes = {};
 
-    Object.keys(constants.SIZES).forEach(function (key) {
-      let size = constants.SIZES[key];
+    Object.keys(styleMaps.SIZES).forEach(function (key) {
+      let size = styleMaps.SIZES[key];
       let prop = size;
       let classPart = size + '-';
 
diff --git a/src/Glyphicon.js b/src/Glyphicon.js
index bb3e41ea19..e406feaa31 100644
--- a/src/Glyphicon.js
+++ b/src/Glyphicon.js
@@ -1,13 +1,13 @@
 import React from 'react';
 import classNames from 'classnames';
 import BootstrapMixin from './BootstrapMixin';
-import constants from './constants';
+import styleMaps from './styleMaps';
 
 const Glyphicon = React.createClass({
   mixins: [BootstrapMixin],
 
   propTypes: {
-    glyph: React.PropTypes.oneOf(constants.GLYPHS).isRequired
+    glyph: React.PropTypes.oneOf(styleMaps.GLYPHS).isRequired
   },
 
   getDefaultProps() {
diff --git a/src/index.js b/src/index.js
index b7e54269fb..ab8c3f01c2 100644
--- a/src/index.js
+++ b/src/index.js
@@ -47,7 +47,7 @@ import Table from './Table';
 import TabPane from './TabPane';
 import Tooltip from './Tooltip';
 import Well from './Well';
-import constants from './constants';
+import styleMaps from './styleMaps';
 
 export default {
   Accordion,
@@ -99,5 +99,5 @@ export default {
   TabPane,
   Tooltip,
   Well,
-  constants
+  styleMaps
 };
diff --git a/src/constants.js b/src/styleMaps.js
similarity index 97%
rename from src/constants.js
rename to src/styleMaps.js
index 02fdc0d057..83435899c6 100644
--- a/src/constants.js
+++ b/src/styleMaps.js
@@ -1,4 +1,4 @@
-export default {
+const styleMaps = {
   CLASSES: {
     'alert': 'alert',
     'button': 'btn',
@@ -31,6 +31,9 @@ export default {
     'tabs': 'tabs',
     'pills': 'pills'
   },
+  addStyle: function(name) {
+    styleMaps.STYLES[name] = name;
+  },
   SIZES: {
     'large': 'lg',
     'medium': 'md',
@@ -299,3 +302,5 @@ export default {
     'menu-up'
   ]
 };
+
+export default styleMaps;
diff --git a/src/utils/CustomPropTypes.js b/src/utils/CustomPropTypes.js
index 73984de7df..c56a0a4e8a 100644
--- a/src/utils/CustomPropTypes.js
+++ b/src/utils/CustomPropTypes.js
@@ -13,7 +13,16 @@ let CustomPropTypes = {
    * @param componentName
    * @returns {Error|undefined}
    */
-  mountable: createMountableChecker()
+  mountable: createMountableChecker(),
+  /**
+   * Checks whether a prop matches a key of an associated object
+   *
+   * @param props
+   * @param propName
+   * @param componentName
+   * @returns {Error|undefined}
+   */
+  keyOf: createKeyOfChecker
 };
 
 /**
@@ -57,4 +66,18 @@ function createMountableChecker() {
   return createChainableTypeChecker(validate);
 }
 
+function createKeyOfChecker(obj) {
+  function validate(props, propName, componentName) {
+    let propValue = props[propName];
+    if (!obj.hasOwnProperty(propValue)) {
+      let valuesString = JSON.stringify(Object.keys(obj));
+      return new Error(
+        `Invalid prop '${propName}' of value '${propValue}' ` +
+        `supplied to '${componentName}', expected one of ${valuesString}.`
+      );
+    }
+  }
+  return createChainableTypeChecker(validate);
+}
+
 export default CustomPropTypes;
diff --git a/test/BootstrapMixinSpec.js b/test/BootstrapMixinSpec.js
index bf6d4fd628..dea0bac9ce 100644
--- a/test/BootstrapMixinSpec.js
+++ b/test/BootstrapMixinSpec.js
@@ -1,6 +1,7 @@
 import React from 'react';
 import ReactTestUtils from 'react/lib/ReactTestUtils';
 import BootstrapMixin from '../src/BootstrapMixin';
+import styleMaps from '../src/styleMaps';
 
 let Component;
 
@@ -195,5 +196,15 @@ describe('BootstrapMixin', function () {
       );
       assert.equal(instance.prefixClass('title'), 'btn-title');
     });
+
+    it('should return "btn btn-wacky"', function () {
+      styleMaps.addStyle('wacky');
+      let instance = ReactTestUtils.renderIntoDocument(
+        <Component bsClass='button' bsStyle='wacky'>
+          content
+        </Component>
+      );
+      assert.deepEqual(instance.getBsClassSet(), {'btn': true, 'btn-wacky': true});
+    });
   });
 });
diff --git a/test/CustomPropTypesSpec.js b/test/CustomPropTypesSpec.js
index 89031672f0..9a0b94deb2 100644
--- a/test/CustomPropTypesSpec.js
+++ b/test/CustomPropTypesSpec.js
@@ -25,4 +25,26 @@ describe('CustomPropTypes', function () {
       assert.isUndefined(validate(ReactTestUtils.renderIntoDocument(<div />)));
     });
   });
+
+  describe('keyOf', function () {
+    let obj = {'foo': 1};
+    function validate(prop) {
+      return CustomPropTypes.keyOf(obj)({p: prop}, 'p', 'Component');
+    }
+    function validateRequired(prop) {
+      return CustomPropTypes.keyOf(obj).isRequired({p: prop}, 'p', 'Component');
+    }
+
+    it('Should return error with non-key values', function() {
+      assert.instanceOf(validateRequired(), Error);
+      assert.instanceOf(validateRequired(null), Error);
+      assert.instanceOf(validate('bar'), Error);
+    });
+    it('Should return undefined with key values', function() {
+      assert.isUndefined(validate());
+      assert.isUndefined(validate('foo'));
+      obj.bar = 2;
+      assert.isUndefined(validate('bar'));
+    });
+  });
 });