diff --git a/packages/babel-helpers/src/helpers.js b/packages/babel-helpers/src/helpers.js
index 99f4ec77e4..71d2e382aa 100644
--- a/packages/babel-helpers/src/helpers.js
+++ b/packages/babel-helpers/src/helpers.js
@@ -428,7 +428,7 @@ helpers.inheritsLoose = defineHelper(`
 // Based on https://github.com/WebReflection/babel-plugin-transform-builtin-classes
 helpers.wrapNativeSuper = defineHelper(`
   var _gPO = Object.getPrototypeOf || function _gPO(o) { return o.__proto__ };
-  var _sPO = Object.setPrototypeOf || function _sPO(o, p) { o.__proto__ = p };
+  var _sPO = Object.setPrototypeOf || function _sPO(o, p) { o.__proto__ = p; return o };
   var _construct = (typeof Reflect === "object" && Reflect.construct) ||
     function _construct(Parent, args, Class) {
       var Constructor, a = [null];
diff --git a/packages/babel-plugin-transform-classes/test/fixtures/extend-builtins/loose/expected.js b/packages/babel-plugin-transform-classes/test/fixtures/extend-builtins/loose/expected.js
index ad11812833..90a34b02cd 100644
--- a/packages/babel-plugin-transform-classes/test/fixtures/extend-builtins/loose/expected.js
+++ b/packages/babel-plugin-transform-classes/test/fixtures/extend-builtins/loose/expected.js
@@ -2,7 +2,7 @@ function _inheritsLoose(subClass, superClass) { subClass.prototype = Object.crea
 
 var _gPO = Object.getPrototypeOf || function _gPO(o) { return o.__proto__; };
 
-var _sPO = Object.setPrototypeOf || function _sPO(o, p) { o.__proto__ = p; };
+var _sPO = Object.setPrototypeOf || function _sPO(o, p) { o.__proto__ = p; return o; };
 
 var _construct = typeof Reflect === "object" && Reflect.construct || function _construct(Parent, args, Class) { var Constructor, a = [null]; a.push.apply(a, args); Constructor = Parent.bind.apply(Parent, a); return _sPO(new Constructor(), Class.prototype); };
 
diff --git a/packages/babel-plugin-transform-classes/test/fixtures/extend-builtins/spec/expected.js b/packages/babel-plugin-transform-classes/test/fixtures/extend-builtins/spec/expected.js
index ae78bb95f7..b6a5b878b7 100644
--- a/packages/babel-plugin-transform-classes/test/fixtures/extend-builtins/spec/expected.js
+++ b/packages/babel-plugin-transform-classes/test/fixtures/extend-builtins/spec/expected.js
@@ -6,7 +6,7 @@ function _inherits(subClass, superClass) { if (typeof superClass !== "function"
 
 var _gPO = Object.getPrototypeOf || function _gPO(o) { return o.__proto__; };
 
-var _sPO = Object.setPrototypeOf || function _sPO(o, p) { o.__proto__ = p; };
+var _sPO = Object.setPrototypeOf || function _sPO(o, p) { o.__proto__ = p; return o; };
 
 var _construct = typeof Reflect === "object" && Reflect.construct || function _construct(Parent, args, Class) { var Constructor, a = [null]; a.push.apply(a, args); Constructor = Parent.bind.apply(Parent, a); return _sPO(new Constructor(), Class.prototype); };