Include *all* object keys, not just enumerable string keys

index.js

@@ -33,7 +33,7 @@ module.exports = function hasShape(rules) {
 
 		let unexpectedPropertyErrors = asExpression(() => {
 			if (!allowExtraProperties) {
-				return Object.keys(object).map((propertyName) => {
+				return Reflect.ownKeys(object).map((propertyName) => {
 					if (!containsRules(rules[propertyName])) {
 						return new ValidationError(`Encountered an unexpected property '${propertyName}'`);
 					} else {
@@ -58,8 +58,8 @@ module.exports = function hasShape(rules) {
 
 			// We need to consider the keys from the ruleset (for detecting missing required properties) *and* the keys from the actual object (for handling extraneous values).
 			let allKeys = arrayUnion(
-				Object.keys(rules),
+				Reflect.ownKeys(rules),
-				Object.keys(object)
+				Reflect.ownKeys(object)
 			);
 
 			for (let key of allKeys) {
@@ -82,6 +82,7 @@ module.exports = function hasShape(rules) {
 					}
 				} else {
 					// Extraneous property
+					// FIXME: Assign non-enumerable if the source property was non-enumerable!
 					newObject[key] = value;
 				}
 			}