diff --git a/lib/iterator.js b/lib/iterator.js
index 3d8e40aa..899c5327 100644
--- a/lib/iterator.js
+++ b/lib/iterator.js
@@ -11,7 +11,9 @@ const toIterator = base => {
 
 class Iterator {
   constructor(base) {
-    this.base = toIterator(base);
+    if (typeof base.next !== 'function')
+      throw new TypeError('Base is not Iterable');
+    this.base = base;
   }
 
   [Symbol.iterator]() {
@@ -490,7 +492,7 @@ class SkipWhileIterator extends Iterator {
   }
 }
 
-const iter = base => new Iterator(base);
+const iter = base => new Iterator(toIterator(base));
 
 module.exports = {
   Iterator,
diff --git a/test/iterator.js b/test/iterator.js
index 390e8381..19149666 100644
--- a/test/iterator.js
+++ b/test/iterator.js
@@ -12,6 +12,11 @@ metatests.test('new Iterator() on non Iterable', test => {
   test.end();
 });
 
+metatests.testSync('new Iterator() on Iterator', test => {
+  const it = array[Symbol.iterator]();
+  test.strictSame(new Iterator(it).toArray(), array);
+});
+
 metatests.test('iter returns an Iterator', test => {
   const iterator = iter(array);
   test.assert(iterator instanceof Iterator);