diff --git a/spec.emu b/spec.emu
index d475853..f602c7a 100644
--- a/spec.emu
+++ b/spec.emu
@@ -16,7 +16,7 @@ copyright: false
       1. Repeat, while _items_ is not empty,
         1. Let _iter_ be the first element of _items_.
         1. Remove the first element from _items_.
-        1. Let _iteratorRecord_ be ? GetIteratorFlattenable(_iter_, ~iterate-strings~).
+        1. Let _iteratorRecord_ be ? GetIteratorFlattenable(_iter_, ~reject-strings~).
         1. Let _innerAlive_ be *true*.
         1. Repeat, while _innerAlive_ is *true*,
           1. Let _innerValue_ be ? IteratorStepValue(_iteratorRecord_).
diff --git a/src/index.ts b/src/index.ts
index 88b7679..63bca7f 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -4,8 +4,6 @@ if (typeof Iterator === 'undefined' || Iterator == null) {
   globalThis.Iterator = function() {};
 }
 
-const IteratorPrototype = Object.getPrototypeOf(Object.getPrototypeOf([].values()))
-
 function getIteratorFlattenable<A>(obj: IteratorOrIterable<A>, stringHandling: 'iterate-strings' | 'reject-strings'): Iterator<A>
 function getIteratorFlattenable(obj: any, stringHandling: 'iterate-strings' | 'reject-strings'): Iterator<unknown>
 function getIteratorFlattenable(obj: any, stringHandling: 'iterate-strings' | 'reject-strings'): Iterator<unknown> {
@@ -44,10 +42,10 @@ function* concatImpl(...iterators: Array<unknown>): Generator<unknown> {
   try {
     for (; i < iterators.length; ++i) {
       let iter = iterators[i];
-      yield* liftIterator(getIteratorFlattenable(iter, 'iterate-strings'));
+      yield* liftIterator(getIteratorFlattenable(iter, 'reject-strings'));
     }
   } finally {
-    let err = null, hasErr = false;;
+    let err = null, hasErr = false;
     for (++i; i < iterators.length; ++i) {
       try {
         let obj = iterators[i];
diff --git a/test/index.mjs b/test/index.mjs
index 71917d7..931a617 100644
--- a/test/index.mjs
+++ b/test/index.mjs
@@ -30,10 +30,11 @@ test('concat', async t => {
   );
 });
 
-test('concat iterates strings', async t => {
-  assert.deepEqual(
-    Array.from(Iterator.concat("ab", "cd")),
-    ["a", "b", "c", "d"],
+test('concat does not iterate strings', async t => {
+  let it = Iterator.concat("ab", "cd");
+  assert.throws(
+    () => Array.from(it),
+    TypeError,
   );
 });
 
@@ -142,4 +143,4 @@ test('closes later iterators', async t => {
     concatted.return();
     assert.deepEqual(returned, ['a', 'b', 'c']);
   });
-});
\ No newline at end of file
+});