diff --git a/lib/net/smtp.rb b/lib/net/smtp.rb
index 13e1f1f..639c01e 100644
--- a/lib/net/smtp.rb
+++ b/lib/net/smtp.rb
@@ -1152,6 +1152,7 @@ def initialize(address, *args, **kw_args)
       def to_s
         @address
       end
+      alias to_str to_s
     end
   end   # class SMTP
 
diff --git a/test/net/smtp/test_smtp.rb b/test/net/smtp/test_smtp.rb
index 9a0ac53..2e29719 100644
--- a/test/net/smtp/test_smtp.rb
+++ b/test/net/smtp/test_smtp.rb
@@ -102,6 +102,8 @@ def test_rcptto_with_address
     def test_address
       a = Net::SMTP::Address.new('foo@example.com', 'p0=123', {p1: 456}, p2: nil, p3: '789')
       assert_equal 'foo@example.com', a.address
+      assert_equal '<foo@example.com>', "<#{a}>" # Address#to_s
+      assert_match(/\Afoo@example\.com\z/, a) # Address#to_str
       assert_equal ['p0=123', 'p1=456', 'p2', 'p3=789'], a.parameters
     end