diff --git a/io.c b/io.c
index a4afeafc60..8a5d6ab246 100644
--- a/io.c
+++ b/io.c
@@ -1637,12 +1637,16 @@ io_writev(int argc, VALUE *argv, VALUE io)
 
     for (i = 0; i < argc; i += cnt) {
 #ifdef HAVE_WRITEV
-	if ((cnt = argc - i) >= IOV_MAX) cnt = IOV_MAX-1;
-	n = io_fwritev(cnt, &argv[i], fptr);
-#else
-	/* sync at last item */
-	n = io_fwrite(argv[i], fptr, (i < argc-1));
+	if ((fptr->mode & (FMODE_SYNC|FMODE_TTY)) && ((cnt = argc - i) < IOV_MAX)) {
+	    n = io_fwritev(cnt, &argv[i], fptr);
+	}
+	else
 #endif
+	{
+	    cnt = 1;
+	    /* sync at last item */
+	    n = io_fwrite(rb_obj_as_string(argv[i]), fptr, (i < argc-1));
+	}
 	if (n == -1L) rb_sys_fail_path(fptr->pathv);
 	total = rb_fix_plus(LONG2FIX(n), total);
     }
diff --git a/test/ruby/test_io.rb b/test/ruby/test_io.rb
index 0bedebfc16..a12cda6277 100644
--- a/test/ruby/test_io.rb
+++ b/test/ruby/test_io.rb
@@ -1274,6 +1274,15 @@ class TestIO < Test::Unit::TestCase
     assert_in_out_err([], "STDOUT.write(:foo, :bar)", ["foobar"])
   end
 
+  def test_write_buffered_with_multiple_arguments
+    out, err, (_, status) = EnvUtil.invoke_ruby(["-e", "sleep 0.1;puts 'foo'"], "", true, true) do |_, o, e, i|
+      [o.read, e.read, Process.waitpid2(i)]
+    end
+    assert_predicate(status, :success?)
+    assert_equal("foo\n", out)
+    assert_empty(err)
+  end
+
   def test_write_non_writable
     with_pipe do |r, w|
       assert_raise(IOError) do