diff --git a/src/Psl/Vec/concat.php b/src/Psl/Vec/concat.php
index 18ac064b..00242770 100644
--- a/src/Psl/Vec/concat.php
+++ b/src/Psl/Vec/concat.php
@@ -9,12 +9,12 @@
  *
  * @template T
  *
- * @param list<T> $first
+ * @param iterable<T> $first
  * @param iterable<T> ...$rest
  *
  * @return list<T>
  */
-function concat(array $first, iterable ...$rest): array
+function concat(iterable $first, iterable ...$rest): array
 {
     $first = values($first);
     foreach ($rest as $arr) {