diff --git a/lib/merge.js b/lib/merge.js
index 132d12500c..0913323747 100644
--- a/lib/merge.js
+++ b/lib/merge.js
@@ -3,8 +3,8 @@
 // Merge two objects, including their prototypes
 function mergePrototypes(to, from) {
 	const prototypes = [...getPrototypes(to), ...getPrototypes(from)];
-	const newPrototype = prototypes.reduce(reducePrototype, {});
-	return Object.assign(Object.setPrototypeOf(to, newPrototype), to, from);
+	const prototype = prototypes.reduce(shallowMerge, {});
+	return Object.assign(Object.setPrototypeOf(to, prototype), from);
 }
 
 function getPrototypes(object, prototypes = []) {
@@ -16,8 +16,8 @@ function getPrototypes(object, prototypes = []) {
 	return prototypes;
 }
 
-function reducePrototype(prototype, constructor) {
-	return Object.defineProperties(prototype, Object.getOwnPropertyDescriptors(constructor));
+function shallowMerge(toObject, fromObject) {
+	return Object.defineProperties(toObject, Object.getOwnPropertyDescriptors(fromObject));
 }
 
 module.exports = mergePrototypes;