diff --git a/.babelrc b/.babelrc
index 11c2e5f..fe082af 100644
--- a/.babelrc
+++ b/.babelrc
@@ -34,7 +34,9 @@
           "babel-runtime/helpers/extends": "./src/polyfills/extends",
           "babel-runtime/helpers/inherits": "./src/polyfills/inherits",
           "babel-runtime/helpers/createClass": "./src/polyfills/createClass",
-          "babel-runtime/helpers/possibleConstructorReturn": "./src/polyfills/possibleConstructorReturn"
+          "babel-runtime/helpers/possibleConstructorReturn": "./src/polyfills/possibleConstructorReturn",
+          "babel-runtime/helpers/classCallCheck": "./src/polyfills/classCallCheck",
+          "babel-runtime/core-js/object/keys": "./src/polyfills/keys"
         }
       }
     ]
diff --git a/src/polyfills/classCallCheck.js b/src/polyfills/classCallCheck.js
new file mode 100644
index 0000000..aa83175
--- /dev/null
+++ b/src/polyfills/classCallCheck.js
@@ -0,0 +1,5 @@
+export default function(instance, Constructor) {
+  if (!(instance instanceof Constructor)) {
+    throw new TypeError('Cannot call a class as a function')
+  }
+}
diff --git a/src/polyfills/keys.js b/src/polyfills/keys.js
new file mode 100644
index 0000000..b683766
--- /dev/null
+++ b/src/polyfills/keys.js
@@ -0,0 +1,38 @@
+// From https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/keys
+var hasOwnProperty = Object.prototype.hasOwnProperty,
+  hasDontEnumBug = !{ toString: null }.propertyIsEnumerable('toString'),
+  dontEnums = [
+    'toString',
+    'toLocaleString',
+    'valueOf',
+    'hasOwnProperty',
+    'isPrototypeOf',
+    'propertyIsEnumerable',
+    'constructor',
+  ],
+  dontEnumsLength = dontEnums.length
+
+export default function(obj) {
+  if (typeof obj !== 'function' && (typeof obj !== 'object' || obj === null)) {
+    throw new TypeError('Object.keys called on non-object')
+  }
+
+  var result = [],
+    prop,
+    i
+
+  for (prop in obj) {
+    if (hasOwnProperty.call(obj, prop)) {
+      result.push(prop)
+    }
+  }
+
+  if (hasDontEnumBug) {
+    for (i = 0; i < dontEnumsLength; i++) {
+      if (hasOwnProperty.call(obj, dontEnums[i])) {
+        result.push(dontEnums[i])
+      }
+    }
+  }
+  return result
+}