diff --git a/spec.emu b/spec.emu
index 554ab7b..d475853 100644
--- a/spec.emu
+++ b/spec.emu
@@ -25,7 +25,20 @@ copyright: false
           1. Else,
             1. Let _completion_ be Completion(Yield(_innerValue_)).
             1. If _completion_ is an abrupt completion, then
-              1. Return ? IteratorClose(_iteratorRecord_, _completion_).
+              1. Set _completion_ to Completion(IteratorClose(_iteratorRecord_, _completion_)).
+              1. Repeat, while _items_ is not empty,
+                1. Let _trailingIter_ be the first element of _items_.
+                1. Remove the first element from _items_.
+                1. If _trailingIter_ is an Object, then
+                  1. Let _nextMethod_ be Completion(Get(_trailingIter_, "next")).
+                  1. If _nextMethod_ is an abrupt completion, then
+                    1. If _completion_ is not a throw completion, set _completion_ to _nextMethod_.
+                  1. Else,
+                    1. Set _nextMethod_ to ! _nextMethod_.
+                    1. If IsCallable(_nextMethod_), then
+                      1. Let _record_ be the Iterator Record { [[Iterator]]: _iter_, [[NextMethod]]: _nextMethod_, [[Done]]: true }.
+                      1. Set _completion_ to Completion(IteratorClose(_iteratorRecord_, _completion_)).
+              1. Return ? _completion_.
     1. Return CreateIteratorFromClosure(_closure_, *"Iterator Helper"*, %IteratorHelperPrototype%, « »).
   </emu-alg>
 </emu-clause>
diff --git a/src/index.ts b/src/index.ts
index a033c65..88b7679 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -40,8 +40,31 @@ function concatImpl<A, B, C, D>(iteratorA: IteratorOrIterable<A>, iteratorB: Ite
 function concatImpl<A, B, C, D, E>(iteratorA: IteratorOrIterable<A>, iteratorB: IteratorOrIterable<B>, iteratorC: IteratorOrIterable<C>, iteratorD: IteratorOrIterable<D>, iteratorE: IteratorOrIterable<E>): Generator<A | B | C | D | E>
 function concatImpl(...iterators: Array<IteratorOrIterable<unknown>>): Generator<unknown>
 function* concatImpl(...iterators: Array<unknown>): Generator<unknown> {
-  for (const iter of iterators) {
-    yield* liftIterator(getIteratorFlattenable(iter, 'iterate-strings'));
+  let i = 0;
+  try {
+    for (; i < iterators.length; ++i) {
+      let iter = iterators[i];
+      yield* liftIterator(getIteratorFlattenable(iter, 'iterate-strings'));
+    }
+  } finally {
+    let err = null, hasErr = false;;
+    for (++i; i < iterators.length; ++i) {
+      try {
+        let obj = iterators[i];
+        if (obj != null && (typeof obj === 'object' || typeof obj === 'function')) {
+          let iter = obj as Iterator<unknown>;
+          if (typeof iter.next === 'function') {
+            iter.return?.();
+          }
+        }
+      } catch (e) {
+        if (!hasErr) {
+          hasErr = true;
+          err = e;
+        }
+      }
+    }
+    if (hasErr) throw err;
   }
 }
 
diff --git a/test/index.mjs b/test/index.mjs
index 0ab53f7..71917d7 100644
--- a/test/index.mjs
+++ b/test/index.mjs
@@ -56,3 +56,90 @@ test('concat bare iterators', async t => {
     [0, 1, 2, 3, 4, 5],
   );
 });
+
+test('closes later iterators', async t => {
+  await t.test('stopped between iterators', () => {
+    let returned = [];
+    let concatted = Iterator.concat(
+      [0, 1],
+      [2, 3],
+      {
+        next() {
+          return { done: false, value: 'a' };
+        },
+        return() {
+          returned.push('a');
+          return { done: true, value: undefined };
+        },
+      },
+      {
+        next() {
+          return { done: false, value: 'b' };
+        },
+        return() {
+          returned.push('b');
+          return { done: true, value: undefined };
+        },
+      },
+      {
+        next() {
+          return { done: false, value: 'c' };
+        },
+        return() {
+          returned.push('c');
+          return { done: true, value: undefined };
+        },
+      },
+    );
+    assert.equal(concatted.next().value, 0);
+    assert.equal(concatted.next().value, 1);
+    assert.equal(concatted.next().value, 2);
+    assert.equal(concatted.next().value, 3);
+    assert.deepEqual(returned, []);
+    concatted.return();
+    assert.deepEqual(returned, ['a', 'b', 'c']);
+  });
+
+  await t.test('stopped during iteration', () => {
+    let returned = [];
+    let concatted = Iterator.concat(
+      [0, 1],
+      [2, 3],
+      {
+        next() {
+          return { done: false, value: 4 };
+        },
+        return() {
+          returned.push('a');
+          return { done: true, value: undefined };
+        },
+      },
+      {
+        next() {
+          return { done: false, value: 'b' };
+        },
+        return() {
+          returned.push('b');
+          return { done: true, value: undefined };
+        },
+      },
+      {
+        next() {
+          return { done: false, value: 'c' };
+        },
+        return() {
+          returned.push('c');
+          return { done: true, value: undefined };
+        },
+      },
+    );
+    assert.equal(concatted.next().value, 0);
+    assert.equal(concatted.next().value, 1);
+    assert.equal(concatted.next().value, 2);
+    assert.equal(concatted.next().value, 3);
+    assert.equal(concatted.next().value, 4);
+    assert.deepEqual(returned, []);
+    concatted.return();
+    assert.deepEqual(returned, ['a', 'b', 'c']);
+  });
+});
\ No newline at end of file