diff --git a/core/string.rbs b/core/string.rbs
index 59d3122d4..947af5e63 100644
--- a/core/string.rbs
+++ b/core/string.rbs
@@ -1623,7 +1623,7 @@ class String
   #
   # Related: see [Modifying](rdoc-ref:String@Modifying).
   #
-  def append_as_bytes: (String) -> String
+  def append_as_bytes: (*String | Integer) -> String
 
   # <!--
   #   rdoc-file=string.c
diff --git a/test/stdlib/String_test.rb b/test/stdlib/String_test.rb
index c9b69f696..7a42d481f 100644
--- a/test/stdlib/String_test.rb
+++ b/test/stdlib/String_test.rb
@@ -301,6 +301,12 @@ def test_append_as_bytes
     if_ruby("3.4"...) do
       assert_send_type  '(String) -> String',
                         'hello', :append_as_bytes, "world"
+      assert_send_type  '(*String) -> String',
+                        'hello', :append_as_bytes, "world", "once", "more"
+      assert_send_type  '(Integer) -> String',
+                        'hello', :append_as_bytes, 0
+      assert_send_type  '(*Integer) -> String',
+                        'hello', :append_as_bytes, 0, 257
     end
   end