diff --git a/src/Latte/Essential/CombineIterator.php b/src/Latte/Essential/CombineIterator.php
new file mode 100644
index 000000000..8c60c30e0
--- /dev/null
+++ b/src/Latte/Essential/CombineIterator.php
@@ -0,0 +1,52 @@
+<?php
+
+/**
+ * This file is part of the Latte (https://latte.nette.org)
+ * Copyright (c) 2008 David Grudl (https://davidgrudl.com)
+ */
+
+declare(strict_types=1);
+
+namespace Latte\Essential;
+
+
+/**
+ * @internal
+ */
+class CombineIterator implements \Iterator
+{
+	public function __construct(
+		private array $pairs,
+	) {
+	}
+
+
+	public function current(): mixed
+	{
+		return current($this->pairs)[1];
+	}
+
+
+	public function key(): mixed
+	{
+		return current($this->pairs)[0];
+	}
+
+
+	public function next(): void
+	{
+		next($this->pairs);
+	}
+
+
+	public function rewind(): void
+	{
+		reset($this->pairs);
+	}
+
+
+	public function valid(): bool
+	{
+		return key($this->pairs) !== null;
+	}
+}
diff --git a/src/Latte/Essential/Filters.php b/src/Latte/Essential/Filters.php
index 0705bcdf5..adf0665d8 100644
--- a/src/Latte/Essential/Filters.php
+++ b/src/Latte/Essential/Filters.php
@@ -458,28 +458,23 @@ public static function sort(iterable $iterable, ?\Closure $comparison = null): i
 			return $iterable;
 		}
 
-		$keys = $values = [];
+		$pairs = [];
 		foreach ($iterable as $key => $value) {
-			$keys[] = $key;
-			$values[] = $value;
+			$pairs[] = [$key, $value];
 		}
-		$comparison ? uasort($values, $comparison) : asort($values);
+		uasort($pairs, fn($a, $b) => $comparison ? $comparison($a[1], $b[1]) : $a[1] <=> $b[1]);
 
-		return (static function () use ($keys, $values): \Generator {
-			foreach ($values as $i => $value) {
-				yield $keys[$i] => $value;
-			}
-		})();
+		return new CombineIterator($pairs);
 	}
 
 
 	/**
 	 * Groups elements by the element indices and preserves the key association and order.
 	 */
-	public static function group(iterable $iterable, string|int|\Closure $by): \Generator
+	public static function group(iterable $iterable, string|int|\Closure $by): \Iterator
 	{
 		$fn = $by instanceof \Closure ? $by : fn($a) => is_array($a) ? $a[$by] : $a->$by;
-		$keys = $groups = $prevKey = [];
+		$keys = $groups = [];
 
 		foreach ($iterable as $k => $v) {
 			$groupKey = $fn($v, $k);
@@ -491,17 +486,14 @@ public static function group(iterable $iterable, string|int|\Closure $by): \Gene
 				}
 				$prevKey = $groupKey;
 			}
-			$groups[$index][0][] = $k;
-			$groups[$index][1][] = $v;
+			$groups[$index][] = [$k, $v];
 		}
 
-		foreach ($groups as $index => $pair) {
-			yield $keys[$index] => (static function () use ($pair): \Generator {
-				foreach ($pair[1] as $i => $value) {
-					yield $pair[0][$i] => $value;
-				}
-			})();
-		}
+		return new CombineIterator(array_map(
+			fn($key, $group) => [$key, new CombineIterator($group)],
+			$keys,
+			$groups,
+		));
 	}
 
 
diff --git a/tests/common/CombineIterator.phpt b/tests/common/CombineIterator.phpt
new file mode 100644
index 000000000..74a0f7fca
--- /dev/null
+++ b/tests/common/CombineIterator.phpt
@@ -0,0 +1,54 @@
+<?php
+
+/**
+ * Test: CombineIterator basic usage.
+ */
+
+declare(strict_types=1);
+
+use Latte\Essential\CombineIterator;
+use Tester\Assert;
+
+require __DIR__ . '/../bootstrap.php';
+
+
+function exportIterator(iterable $iterator): array
+{
+	$res = [];
+	foreach ($iterator as $key => $value) {
+		$res[] = [$key, $value];
+	}
+	return $res;
+}
+
+
+test('empty array', function () {
+	Assert::same(
+		[],
+		exportIterator(new CombineIterator([], [])),
+	);
+});
+
+
+test('single usage', function () {
+	$arr = [[new stdClass, new stdClass], [null, null]];
+	$iterator = new CombineIterator(array_column($arr, 0), array_column($arr, 1));
+	Assert::same(
+		$arr,
+		exportIterator($iterator),
+	);
+});
+
+
+test('double usage', function () {
+	$arr = [[new stdClass, new stdClass], [null, null]];
+	$iterator = new CombineIterator(array_column($arr, 0), array_column($arr, 1));
+	Assert::same(
+		$arr,
+		exportIterator($iterator),
+	);
+	Assert::same(
+		$arr,
+		exportIterator($iterator),
+	);
+});
diff --git a/tests/filters/group.phpt b/tests/filters/group.phpt
index ac86d3685..8aeb34e61 100644
--- a/tests/filters/group.phpt
+++ b/tests/filters/group.phpt
@@ -15,8 +15,8 @@ require __DIR__ . '/../bootstrap.php';
 function iterator(): Generator
 {
 	yield ['a' => 55] => ['k' => 22, 'k2'];
-	yield ['a' => 66] => (object) ['k' => 22, 'k2'];
 	yield ['a' => 77] => ['k' => 11];
+	yield ['a' => 66] => (object) ['k' => 22, 'k2'];
 	yield ['a' => 88] => ['k' => 33];
 }
 
@@ -65,6 +65,35 @@ test('iterator', function () {
 });
 
 
+test('multiple calls', function () {
+	$groups = Filters::group(iterator(), 'k');
+
+	Assert::equal(
+		[
+			[22, [
+				[['a' => 55], ['k' => 22, 'k2']],
+				[['a' => 66], (object) ['k' => 22, 'k2']],
+			]],
+			[11, [[['a' => 77], ['k' => 11]]]],
+			[33, [[['a' => 88], ['k' => 33]]]],
+		],
+		exportIterator($groups),
+	);
+
+	Assert::equal(
+		[
+			[22, [
+				[['a' => 55], ['k' => 22, 'k2']],
+				[['a' => 66], (object) ['k' => 22, 'k2']],
+			]],
+			[11, [[['a' => 77], ['k' => 11]]]],
+			[33, [[['a' => 88], ['k' => 33]]]],
+		],
+		exportIterator($groups),
+	);
+});
+
+
 test('array + callback', function () {
 	Assert::same(
 		[[220, [[0, 22]]], [110, [[1, 11]]], [330, [[2, 33]]]],
diff --git a/tests/filters/sort.phpt b/tests/filters/sort.phpt
index 99d62cd6f..0301cd094 100644
--- a/tests/filters/sort.phpt
+++ b/tests/filters/sort.phpt
@@ -44,6 +44,21 @@ test('iterator', function () {
 });
 
 
+test('multiple calls', function () {
+	$sorted = Filters::sort(iterator());
+
+	Assert::same(
+		[['b', 10], ['a', 20], [[true], 30]],
+		exportIterator($sorted),
+	);
+
+	Assert::same(
+		[['b', 10], ['a', 20], [[true], 30]],
+		exportIterator($sorted),
+	);
+});
+
+
 test('user comparison + array', function () {
 	Assert::same(
 		[2 => 30, 0 => 20, 1 => 10],