diff --git a/packages/npm/es-iterator-helpers/Iterator.concat/implementation.js b/packages/npm/es-iterator-helpers/Iterator.concat/implementation.js
index a9a814e4..6ef1b193 100644
--- a/packages/npm/es-iterator-helpers/Iterator.concat/implementation.js
+++ b/packages/npm/es-iterator-helpers/Iterator.concat/implementation.js
@@ -21,11 +21,9 @@ module.exports =
   typeof IteratorConcat === 'function'
     ? IteratorConcat
     : function concat(...iterables) {
-        // ECMAScript Standard Built-in Objects
+        // Built-in functions that are not identified as constructors do
+        // not implement [[Construct]] unless otherwise specified.
         // https://tc39.es/ecma262/#sec-ecmascript-standard-built-in-objects
-        // Built-in function objects that are not identified as constructors do
-        // not implement the [[Construct]] internal method unless otherwise
-        // specified in the description of a particular function.
         if (new.target) {
           throw new TypeErrorCtor('`Iterator.concat` is not a constructor')
         }
@@ -36,8 +34,15 @@ module.exports =
         for (let i = 0; i < length; i += 1) {
           const iterable = iterables[i]
           // Step 2.a: If item is not an Object, throw a TypeError exception.
+          ensureObject(iterable, 'iterable')
           // Step 2.b: Let method be GetMethod(item, %Symbol.iterator%).
+          const method = getMethod(iterable, SymbolIterator)
           // Step 2.c: If method is undefined, throw a TypeError exception.
+          if (method === undefined) {
+            throw new TypeErrorCtor(
+              '`Iterator.concat` requires all arguments to be iterable'
+            )
+          }
           // (Handled by getMethod, which throws if method is missing or not callable.)
           records[i] = {
             iterable,
@@ -45,28 +50,32 @@ module.exports =
           }
         }
         let index = 0
+        let innerIterator = null
         // Step 3: Let closure be a new Abstract Closure that captures iterables.
         const closure = {
           // This closure will perform the steps defined in Step 3.a.
           next() {
-            const { length } = records
             while (index < length) {
-              const { iterable, openMethod } = records[index]
-              // Step 3.a.i: Let iter be Call(iterable.[[OpenMethod]], iterable.[[Iterable]]).
-              const iterator = ReflectApply(openMethod, iterable, [])
-              // Step 3.a.ii: If iter is not an Object, throw a TypeError exception.
-              ensureObject(iterator)
+              if (!innerIterator) {
+                // If we haven't initialized an inner iterator yet, do so
+                const { iterable, openMethod } = records[index]
+                // Step 3.a.i: Let iter be Call(iterable.[[OpenMethod]], iterable.[[Iterable]]).
+                innerIterator = ReflectApply(openMethod, iterable, [])
+                // Step 3.a.ii: If iter is not an Object, throw a TypeError exception.
+                ensureObject(innerIterator, 'iterator')
+              }
               // Step 3.a.iii: Let iteratorRecord be GetIteratorDirect(iter).
-              const { next } = getIteratorDirect(iterator)
+              const { next } = getIteratorDirect(innerIterator)
               // Step 3.a.iv: Let innerAlive be true.
               // (Handled by the loop structure)
               // Step 3.a.v: Repeat, while innerAlive is true.
-              const result = ReflectApply(next, iterator, [])
+              const result = ReflectApply(next, innerIterator, [])
               if (!result.done) {
                 // Step 3.a.v.3.a: Yield the value of the iterator.
                 return result
               }
               // Step 3.a.v.2: If innerValue is done, move to the next iterable.
+              innerIterator = null
               index += 1
             }
             // Step 3.b: Return Completion(undefined).
diff --git a/packages/npm/es-iterator-helpers/Iterator.concat/polyfill.js b/packages/npm/es-iterator-helpers/Iterator.concat/polyfill.js
index c69f248e..ff68a60c 100644
--- a/packages/npm/es-iterator-helpers/Iterator.concat/polyfill.js
+++ b/packages/npm/es-iterator-helpers/Iterator.concat/polyfill.js
@@ -1,8 +1,7 @@
 'use strict'
 
 const impl = require('./implementation')
-const Iterator = require('../Iterator/implementation')
 
 module.exports = function getPolyfill() {
-  return typeof Iterator.concat === 'function' ? Iterator.concat : impl
+  return impl
 }
diff --git a/packages/npm/es-iterator-helpers/Iterator.concat/shim.js b/packages/npm/es-iterator-helpers/Iterator.concat/shim.js
index e2123812..9e3fc006 100644
--- a/packages/npm/es-iterator-helpers/Iterator.concat/shim.js
+++ b/packages/npm/es-iterator-helpers/Iterator.concat/shim.js
@@ -1,14 +1,14 @@
 'use strict'
 
 const getPolyfill = require('./polyfill')
-const Iterator = require('../Iterator/implementation')
+const IteratorCtor = require('../Iterator/implementation')
 
 const { defineProperty: ObjectDefineProperty } = Object
 
 module.exports = function shimIteratorConcat() {
   const polyfill = getPolyfill()
-  if (Iterator.concat !== polyfill) {
-    ObjectDefineProperty(Iterator, 'concat', {
+  if (IteratorCtor.concat !== polyfill) {
+    ObjectDefineProperty(IteratorCtor, 'concat', {
       __proto__: null,
       configurable: true,
       enumerable: false,
diff --git a/packages/npm/es-iterator-helpers/Iterator.from/implementation.js b/packages/npm/es-iterator-helpers/Iterator.from/implementation.js
index dfa9b8d2..ffb8d24d 100644
--- a/packages/npm/es-iterator-helpers/Iterator.from/implementation.js
+++ b/packages/npm/es-iterator-helpers/Iterator.from/implementation.js
@@ -1,23 +1,41 @@
 'use strict'
 
+const IteratorCtor = require('../Iterator/implementation')
 const {
-  ReflectApply,
+  IteratorCtor: IteratorCtorRaw,
+  ObjectCreate,
   TypeErrorCtor,
-  createIteratorFromClosure,
+  WrapForValidIteratorPrototype,
   getIteratorFlattenable,
-  setUnderlyingIterator
+  setIterated
 } = require('../shared')
 
-module.exports = function from(O) {
-  if (new.target) {
-    throw new TypeErrorCtor('`Iterator.from` is not a constructor')
-  }
-  const { iterator, next } = getIteratorFlattenable(O)
-  const wrapper = createIteratorFromClosure({
-    next() {
-      return ReflectApply(next, iterator, [])
-    }
-  })
-  setUnderlyingIterator(wrapper, iterator)
-  return wrapper
-}
+const IteratorFrom = IteratorCtorRaw?.from
+
+// Based specification text:
+// https://tc39.es/ecma262/#sec-iterator.from
+module.exports =
+  typeof IteratorFrom === 'function'
+    ? IteratorFrom
+    : function from(O) {
+        // Built-in functions that are not identified as constructors do
+        // not implement [[Construct]] unless otherwise specified.
+        // https://tc39.es/ecma262/#sec-ecmascript-standard-built-in-objects
+        if (new.target) {
+          throw new TypeErrorCtor('`Iterator.from` is not a constructor')
+        }
+        // Step 1: Let iteratorRecord be GetIteratorFlattenable(O, iterate-string-primitives).
+        const { iterator, next } = getIteratorFlattenable(O, true)
+        // Step 2: Let hasInstance be OrdinaryHasInstance(%Iterator%, iteratorRecord.[[Iterator]]).
+        // Step 3: If hasInstance is true, then
+        if (iterator instanceof IteratorCtor) {
+          // Step 3.a: Return iteratorRecord.[[Iterator]].
+          return iterator
+        }
+        // Step 4: Let wrapper be OrdinaryObjectCreate(%WrapForValidIteratorPrototype%, << [[Iterated]] >>).
+        const wrapper = ObjectCreate(WrapForValidIteratorPrototype)
+        // Step 5: Set wrapper.[[Iterated]] to iteratorRecord.
+        setIterated(wrapper, { iterator, next })
+        // Step 6: Return wrapper.
+        return wrapper
+      }
diff --git a/packages/npm/es-iterator-helpers/Iterator.from/shim.js b/packages/npm/es-iterator-helpers/Iterator.from/shim.js
index 12208b34..82f1fbc8 100644
--- a/packages/npm/es-iterator-helpers/Iterator.from/shim.js
+++ b/packages/npm/es-iterator-helpers/Iterator.from/shim.js
@@ -1,14 +1,14 @@
 'use strict'
 
 const getPolyfill = require('./polyfill')
-const Iterator = require('../Iterator/implementation')
+const IteratorCtor = require('../Iterator/implementation')
 
 const { defineProperty: ObjectDefineProperty } = Object
 
 module.exports = function shimIteratorFrom() {
   const polyfill = getPolyfill()
   if (Iterator.from !== polyfill) {
-    ObjectDefineProperty(Iterator, 'from', {
+    ObjectDefineProperty(IteratorCtor, 'from', {
       __proto__: null,
       configurable: true,
       enumerable: false,
diff --git a/packages/npm/es-iterator-helpers/Iterator.prototype.drop/implementation.js b/packages/npm/es-iterator-helpers/Iterator.prototype.drop/implementation.js
index 451d2b52..8179e1ba 100644
--- a/packages/npm/es-iterator-helpers/Iterator.prototype.drop/implementation.js
+++ b/packages/npm/es-iterator-helpers/Iterator.prototype.drop/implementation.js
@@ -16,11 +16,9 @@ const {
 // Based specification text:
 // https://tc39.es/ecma262/#sec-iterator.prototype.drop
 module.exports = function drop(limit) {
-  // ECMAScript Standard Built-in Objects
+  // Built-in functions that are not identified as constructors do
+  // not implement [[Construct]] unless otherwise specified.
   // https://tc39.es/ecma262/#sec-ecmascript-standard-built-in-objects
-  // Built-in function objects that are not identified as constructors do
-  // not implement the [[Construct]] internal method unless otherwise
-  // specified in the description of a particular function.
   if (new.target) {
     throw new TypeErrorCtor('`drop` is not a constructor')
   }
diff --git a/packages/npm/es-iterator-helpers/Iterator.prototype.filter/implementation.js b/packages/npm/es-iterator-helpers/Iterator.prototype.filter/implementation.js
index b251cf2e..2737ea3f 100644
--- a/packages/npm/es-iterator-helpers/Iterator.prototype.filter/implementation.js
+++ b/packages/npm/es-iterator-helpers/Iterator.prototype.filter/implementation.js
@@ -13,11 +13,9 @@ const {
 // Based specification text:
 // https://tc39.es/ecma262/#sec-iterator.prototype.filter
 module.exports = function filter(predicate) {
-  // ECMAScript Standard Built-in Objects
+  // Built-in functions that are not identified as constructors do
+  // not implement [[Construct]] unless otherwise specified.
   // https://tc39.es/ecma262/#sec-ecmascript-standard-built-in-objects
-  // Built-in function objects that are not identified as constructors do
-  // not implement the [[Construct]] internal method unless otherwise
-  // specified in the description of a particular function.
   if (new.target) {
     throw new TypeErrorCtor('`filter` is not a constructor')
   }
diff --git a/packages/npm/es-iterator-helpers/Iterator.prototype.flatMap/implementation.js b/packages/npm/es-iterator-helpers/Iterator.prototype.flatMap/implementation.js
index 0980f819..5f7490ff 100644
--- a/packages/npm/es-iterator-helpers/Iterator.prototype.flatMap/implementation.js
+++ b/packages/npm/es-iterator-helpers/Iterator.prototype.flatMap/implementation.js
@@ -14,11 +14,9 @@ const {
 } = require('../shared')
 
 module.exports = function flatMap(mapper) {
-  // ECMAScript Standard Built-in Objects
+  // Built-in functions that are not identified as constructors do
+  // not implement [[Construct]] unless otherwise specified.
   // https://tc39.es/ecma262/#sec-ecmascript-standard-built-in-objects
-  // Built-in function objects that are not identified as constructors do
-  // not implement the [[Construct]] internal method unless otherwise
-  // specified in the description of a particular function.
   if (new.target) {
     throw new TypeErrorCtor('`flatMap` is not a constructor')
   }
diff --git a/packages/npm/es-iterator-helpers/Iterator.prototype.map/implementation.js b/packages/npm/es-iterator-helpers/Iterator.prototype.map/implementation.js
index ec1e4e17..a0de1093 100644
--- a/packages/npm/es-iterator-helpers/Iterator.prototype.map/implementation.js
+++ b/packages/npm/es-iterator-helpers/Iterator.prototype.map/implementation.js
@@ -13,11 +13,9 @@ const {
 // Based on the specification text:
 // https://tc39.es/ecma262/#sec-iterator.prototype.map
 module.exports = function map(mapper) {
-  // ECMAScript Standard Built-in Objects
+  // Built-in functions that are not identified as constructors do
+  // not implement [[Construct]] unless otherwise specified.
   // https://tc39.es/ecma262/#sec-ecmascript-standard-built-in-objects
-  // Built-in function objects that are not identified as constructors do
-  // not implement the [[Construct]] internal method unless otherwise
-  // specified in the description of a particular function.
   if (new.target) {
     throw new TypeErrorCtor('`Iterator.map` is not a constructor')
   }
diff --git a/packages/npm/es-iterator-helpers/Iterator.prototype.toArray/implementation.js b/packages/npm/es-iterator-helpers/Iterator.prototype.toArray/implementation.js
index 60873f2e..624401e1 100644
--- a/packages/npm/es-iterator-helpers/Iterator.prototype.toArray/implementation.js
+++ b/packages/npm/es-iterator-helpers/Iterator.prototype.toArray/implementation.js
@@ -8,17 +8,29 @@ const {
 } = require('../shared')
 
 module.exports = function toArray() {
+  // Built-in functions that are not identified as constructors do
+  // not implement [[Construct]] unless otherwise specified.
+  // https://tc39.es/ecma262/#sec-ecmascript-standard-built-in-objects
   if (new.target) {
     throw new TypeErrorCtor('`toArray` is not a constructor')
   }
-  ensureObject(this)
+  // Step 1: Let O be the this value.
+  const O = this
+  // Step 2: If O is not an Object, throw a TypeError exception.
+  ensureObject(O)
+  // Step 3: Let iterated be GetIteratorDirect(O).
   const { iterator, next } = getIteratorDirect(this)
+  // Step 4: Let items be a new empty List.
   const items = []
+  // Step 5: Repeat.
   while (true) {
+    // Step 5.a: Let value be IteratorStepValue(iterated).
     const result = ReflectApply(next, iterator, [])
+    // Step 5.b: If value is done, return CreateArrayFromList(items).
     if (result.done) {
       return items
     }
+    // Step 5.c: Append value to items.
     items[items.length] = result.value
   }
 }
diff --git a/packages/npm/es-iterator-helpers/Iterator.prototype/shim.js b/packages/npm/es-iterator-helpers/Iterator.prototype/shim.js
index 8078d510..2dc2f6b8 100644
--- a/packages/npm/es-iterator-helpers/Iterator.prototype/shim.js
+++ b/packages/npm/es-iterator-helpers/Iterator.prototype/shim.js
@@ -1,14 +1,14 @@
 'use strict'
 
 const getPolyfill = require('./polyfill')
-const Iterator = require('../Iterator/implementation')
+const IteratorCtor = require('../Iterator/implementation')
 
 const { defineProperty: ObjectDefineProperty } = Object
 
 module.exports = function shimIteratorProto() {
   const polyfill = getPolyfill()
-  if (Iterator.prototype !== polyfill) {
-    ObjectDefineProperty(Iterator, 'prototype', {
+  if (IteratorCtor.prototype !== polyfill) {
+    ObjectDefineProperty(IteratorCtor, 'prototype', {
       __proto__: null,
       configurable: true,
       enumerable: false,
diff --git a/packages/npm/es-iterator-helpers/shared.d.ts b/packages/npm/es-iterator-helpers/shared.d.ts
index 30b369b2..20d03769 100644
--- a/packages/npm/es-iterator-helpers/shared.d.ts
+++ b/packages/npm/es-iterator-helpers/shared.d.ts
@@ -1,22 +1,32 @@
-declare interface IteratorResult<T> {
-  value: T
-  done: boolean
-}
 declare interface Iterator<T> {
   next(value?: any): IteratorResult<T>
   return?(value?: any): IteratorResult<T>
   [Symbol.iterator](): Iterator<T>
 }
+declare interface IteratorHelper<T> extends Iterator<T> {
+  [Symbol.toStringTag](): 'Iterator Helper'
+}
+declare interface IteratorRecord<T> {
+  iterator: Iterator<T>
+  next: () => IteratorResult<T>
+}
+declare interface IteratorResult<T> {
+  value: T
+  done: boolean
+}
 declare interface InternalShared {
   SLOT: WeakMap<any, any>
   SLOT_GENERATOR_CONTEXT: string
   SLOT_GENERATOR_STATE: string
+  SLOT_ITERATED: string
   SLOT_UNDERLYING_ITERATOR: string
   GENERATOR_STATE_COMPLETED: string
   GENERATOR_STATE_SUSPENDED_STARTED: string
   IteratorCtor: typeof globalThis.Iterator
-  IteratorPrototype: any
-  IteratorHelperPrototype: any
+  ArrayCtor: ArrayConstructor
+  IteratorPrototype: Iterator<any>
+  IteratorHelperPrototype: IteratorHelper<any>
+  WrapForValidIteratorPrototype: Iterator<any>
   NumberCtor: NumberConstructor
   MathTrunc: (x: number) => number
   NegativeInfinity: number
@@ -30,17 +40,11 @@ declare interface InternalShared {
   SymbolToStringTag: symbol
   TypeErrorCtor: typeof TypeError
   abruptCloseIterator(iterator: Iterator<any>, error: any): void
-  closeIterator<T>(iterator: Iterator<any>, completion: T): T
+  closeIterator<T>(iterator: Iterator<T>, completion: T): T
   createIteratorFromClosure<T>(closure: Iterator<T>): Iterator<T>
   ensureObject(thisArg: any, what?: string): void
-  getIteratorDirect<T>(obj: any): {
-    next: () => IteratorResult<T>
-    iterator: Iterator<T>
-  }
-  getIteratorFlattenable(obj: any): {
-    next: () => IteratorResult<any>
-    iterator: Iterator<any>
-  }
+  getIteratorDirect<T>(obj: any): IteratorRecord<T>
+  getIteratorFlattenable(obj: any): IteratorRecord<any>
   getMethod(
     obj: any,
     key: string | symbol
@@ -53,7 +57,8 @@ declare interface InternalShared {
   isObjectType(value: any): boolean
   resolveSlots(O: any, slot: string): any
   setSlot(O: any, slot: string, value: any): void
-  setUnderlyingIterator(generator: any, iterator: any): void
+  setUnderlyingIterator(generator: Iterator<any>, iterator: Iterator<any>): void
+  setIterated(wrapper: Iterator<any>, record: IteratorRecord<any>): void
   toIntegerOrInfinity(value: any): number
 }
 declare const shared: InternalShared
diff --git a/packages/npm/es-iterator-helpers/shared.js b/packages/npm/es-iterator-helpers/shared.js
index e2aba35b..cdd57e23 100644
--- a/packages/npm/es-iterator-helpers/shared.js
+++ b/packages/npm/es-iterator-helpers/shared.js
@@ -1,9 +1,14 @@
 'use strict'
 
 //const { toString: fnToStr } = Function.prototype
+const ArrayCtor = Array
 const { trunc: MathTrunc } = Math
 const { isNaN: NumberIsNaN } = Number
-const { create: ObjectCreate, defineProperty: ObjectDefineProperty } = Object
+const {
+  create: ObjectCreate,
+  defineProperty: ObjectDefineProperty,
+  hasOwn: ObjectHasOwn
+} = Object
 const { apply: ReflectApply, getPrototypeOf: ReflectGetPrototypeOf } = Reflect
 const { iterator: SymbolIterator, toStringTag: SymbolToStringTag } = Symbol
 const NumberCtor = Number
@@ -12,8 +17,9 @@ const RangeErrorCtor = RangeError
 
 const SLOT = new WeakMap()
 
-const SLOT_GENERATOR_CONTEXT = '[[generator]]'
+const SLOT_GENERATOR_CONTEXT = '[[GeneratorContext]]'
 const SLOT_GENERATOR_STATE = '[[GeneratorState]]'
+const SLOT_ITERATED = '[[Iterated]]'
 const SLOT_UNDERLYING_ITERATOR = '[[UnderlyingIterator]]'
 
 const GENERATOR_STATE_COMPLETED = 'completed'
@@ -22,6 +28,9 @@ const GENERATOR_STATE_SUSPENDED_STARTED = 'suspended-start'
 const ArrayIteratorPrototype = ReflectGetPrototypeOf([][SymbolIterator]())
 const { Iterator: IteratorCtor } = globalThis
 const IteratorPrototype = ReflectGetPrototypeOf(ArrayIteratorPrototype)
+
+// Based on specification text:
+// https://tc39.es/ecma262/#sec-%iteratorhelperprototype%-object
 const IteratorHelperPrototype = ObjectCreate(IteratorPrototype, {
   next: {
     __proto__: null,
@@ -92,6 +101,64 @@ const IteratorHelperPrototype = ObjectCreate(IteratorPrototype, {
   }
 })
 
+// Based on specification text:
+// https://tc39.es/ecma262/#sec-%wrapforvaliditeratorprototype%-object
+const WrapForValidIteratorPrototype = ObjectCreate(IteratorPrototype, {
+  // Based on specification text:
+  // https://tc39.es/ecma262/#sec-%wrapforvaliditeratorprototype%.next
+  next: {
+    __proto__: null,
+    configurable: true,
+    enumerable: false,
+    value: function next() {
+      // Step 1: Let O be this value.
+      const O = this
+      // Step 2: Perform RequireInternalSlot(O, [[Iterated]])
+      ensureObject(O)
+      const slots = SLOT.get(O)
+      if (!(slots && ObjectHasOwn(slots, SLOT_ITERATED))) {
+        throw new TypeError(`"${SLOT_ITERATED}" is not present on "O"`)
+      }
+      // Step 3: Let iteratorRecord be O.[[Iterated]].
+      const { iterator, next } = slots[SLOT_ITERATED]
+      // Step 4: Return Call(iteratorRecord.[[NextMethod]], iteratorRecord.[[Iterator]]).
+      return ReflectApply(next, iterator, [])
+    },
+    writable: true
+  },
+  // Based on specification text:
+  // https://tc39.es/ecma262/#sec-%wrapforvaliditeratorprototype%.return
+  return: {
+    __proto__: null,
+    configurable: true,
+    enumerable: false,
+    value: function () {
+      // Step 1: Let O be this value.
+      const O = this
+      // Step 2: Perform RequireInternalSlot(O, [[Iterated]]).
+      ensureObject(O)
+      const slots = SLOT.get(O)
+      if (!(slots && ObjectHasOwn(slots, SLOT_ITERATED))) {
+        throw new TypeError(`"${SLOT_ITERATED}" is not present on "O"`)
+      }
+      // Step 3: Let iterator be O.[[Iterated]].[[Iterator]].
+      const { iterator } = slots[SLOT_ITERATED]
+      // Step 4: Assert: iterator is an Object.
+      ensureObject(iterator, 'iterator')
+      // Step 5: Let returnMethod be GetMethod(iterator, "return").
+      const returnMethod = getMethod(iterator, 'return')
+      // Step 6: If returnMethod is undefined, then
+      if (returnMethod === undefined) {
+        // Step 6.a: Return CreateIteratorResultObject(undefined, true).
+        return { value: undefined, done: true }
+      }
+      // Step 7: Return Call(returnMethod, iterator).
+      return ReflectApply(returnMethod, iterator, [])
+    },
+    writable: true
+  }
+})
+
 // Based on specification text:
 // https://tc39.es/ecma262/#sec-ifabruptcloseiterator
 function abruptCloseIterator(iterator, error) {
@@ -157,9 +224,9 @@ function getIteratorDirect(obj) {
 
 // Based on specification text:
 // https://tc39.es/ecma262/#sec-getiteratorflattenable
-function getIteratorFlattenable(obj) {
+function getIteratorFlattenable(obj, allowStrings) {
   // Step 1: If obj is not an Object
-  if (!isObjectType(obj)) {
+  if (!isObjectType(obj) && !(allowStrings && typeof obj === 'string')) {
     // Step 1.a: If primitiveHandling is reject-primitives, throw a TypeError
     throw new TypeErrorCtor('Primitives are not iterable')
   }
@@ -236,6 +303,10 @@ function setSlot(O, slot, value) {
   slots[slot] = value
 }
 
+function setIterated(wrapper, record) {
+  setSlot(wrapper, SLOT_ITERATED, record)
+}
+
 function setUnderlyingIterator(generator, iterator) {
   setSlot(generator, SLOT_UNDERLYING_ITERATOR, iterator)
 }
@@ -259,6 +330,7 @@ function toIntegerOrInfinity(value) {
 }
 
 module.exports = {
+  ArrayCtor,
   IteratorCtor,
   IteratorPrototype,
   NumberCtor,
@@ -270,6 +342,7 @@ module.exports = {
   ReflectGetPrototypeOf,
   SymbolIterator,
   TypeErrorCtor,
+  WrapForValidIteratorPrototype,
   abruptCloseIterator,
   closeIterator,
   createIteratorFromClosure,
@@ -279,6 +352,7 @@ module.exports = {
   getMethod,
   isIteratorProtoNextCheckBuggy,
   isObjectType,
+  setIterated,
   setUnderlyingIterator,
   toIntegerOrInfinity
 }
diff --git a/packages/npm/object.groupby/implementation.js b/packages/npm/object.groupby/implementation.js
index c0ad6d2d..b60262fc 100644
--- a/packages/npm/object.groupby/implementation.js
+++ b/packages/npm/object.groupby/implementation.js
@@ -65,8 +65,8 @@ module.exports =
           }
           const iterator = ReflectApply(method, items, [])
           if (
-            typeof iterator !== 'function' &&
-            (iterator === null || typeof iterator !== 'object')
+            iterator === null ||
+            (typeof iterator !== 'object' && typeof iterator !== 'function')
           ) {
             throw new TypeErrorCtor('`iterator` value must be an Object')
           }
diff --git a/scripts/constants.js b/scripts/constants.js
index 0b54eaca..753ef255 100644
--- a/scripts/constants.js
+++ b/scripts/constants.js
@@ -451,10 +451,10 @@ const skipTestsByEcosystem = Object.freeze({
     // testing ourselves.
     'array-flatten',
     // date tests fail for some Node versions and platforms, but pass in CI
-    // environments for the time being.
+    // Win32 environments for the time being.
     // https://github.com/es-shims/Date/issues/3
     // https://github.com/es-shims/Date/tree/v2.0.5
-    ...(ENV.CI ? [] : ['date']),
+    ...(ENV.WIN_32 ? [] : ['date']),
     // es6-object-assign has no unit tests.
     // https://github.com/rubennorte/es6-object-assign/tree/v1.1.0
     'es6-object-assign',