diff --git a/src/clone-element.js b/src/clone-element.js
index 4cff226275..e10050fdcd 100644
--- a/src/clone-element.js
+++ b/src/clone-element.js
@@ -13,10 +13,21 @@ export function cloneElement(vnode, props, children) {
 		key,
 		ref,
 		i;
+
+	let defaultProps;
+
+	if (vnode.type && vnode.type.defaultProps) {
+		defaultProps = vnode.type.defaultProps;
+	}
+
 	for (i in props) {
 		if (i == 'key') key = props[i];
 		else if (i == 'ref') ref = props[i];
-		else normalizedProps[i] = props[i];
+		else if (props[i] === undefined && defaultProps !== undefined) {
+			normalizedProps[i] = defaultProps[i];
+		} else {
+			normalizedProps[i] = props[i];
+		}
 	}
 
 	if (arguments.length > 2) {
@@ -31,4 +42,4 @@ export function cloneElement(vnode, props, children) {
 		ref || vnode.ref,
 		null
 	);
-}
+}
\ No newline at end of file
diff --git a/src/create-context.js b/src/create-context.js
index df939ee325..4032e626de 100644
--- a/src/create-context.js
+++ b/src/create-context.js
@@ -52,7 +52,10 @@ export function createContext(defaultValue, contextId) {
 					subs.push(c);
 					let old = c.componentWillUnmount;
 					c.componentWillUnmount = () => {
-						subs.splice(subs.indexOf(c), 1);
+						// Patch: this is a hot path, and taking sub out of the array is much
+						// faster this way since it's an unordered list.
+						subs[subs.indexOf(c)] = subs[subs.length - 1];
+						subs.pop();
 						if (old) old.call(c);
 					};
 				};