diff --git a/src/Framework/Assert.php b/src/Framework/Assert.php
index 6ed4b6dfd69..42889f79e63 100644
--- a/src/Framework/Assert.php
+++ b/src/Framework/Assert.php
@@ -527,9 +527,10 @@ final public static function assertContainsOnlyString(iterable $haystack, string
 
     /**
      * Asserts that a haystack contains only instances of a specified interface or class name.
-     *
-     * @param class-string    $className
-     * @param iterable<mixed> $haystack
+     * @template T
+     * @phpstan-assert iterable<T> $haystack
+     * @param class-string<T>      $className
+     * @param iterable<mixed>      $haystack
      *
      * @throws Exception
      * @throws ExpectationFailedException
diff --git a/src/Framework/Assert/Functions.php b/src/Framework/Assert/Functions.php
index cfe2557e300..9207d3ff2b9 100644
--- a/src/Framework/Assert/Functions.php
+++ b/src/Framework/Assert/Functions.php
@@ -537,8 +537,10 @@ function assertContainsOnlyString(iterable $haystack, string $message = ''): voi
     /**
      * Asserts that a haystack contains only instances of a specified interface or class name.
      *
-     * @param class-string    $className
-     * @param iterable<mixed> $haystack
+     * @template T
+     * @phpstan-assert iterable<T> $haystack
+     * @param class-string<T>      $className
+     * @param iterable<mixed>      $haystack
      *
      * @throws Exception
      * @throws ExpectationFailedException