diff --git a/lib/net/smtp.rb b/lib/net/smtp.rb
index cca06e6..52db64e 100644
--- a/lib/net/smtp.rb
+++ b/lib/net/smtp.rb
@@ -33,16 +33,12 @@ module SMTPError
     def initialize(response, message: nil)
       if response.is_a?(::Net::SMTP::Response)
         @response = response
-        @message = message
+        super(message || response.message)
       else
         @response = nil
-        @message = message || response
+        super(message || response)
       end
     end
-
-    def message
-      @message || response.message
-    end
   end
 
   # Represents an SMTP authentication error.
diff --git a/test/net/smtp/test_response.rb b/test/net/smtp/test_response.rb
index 3cf909a..6315db9 100644
--- a/test/net/smtp/test_response.rb
+++ b/test/net/smtp/test_response.rb
@@ -95,6 +95,14 @@ def test_default_exception
         res = Response.parse("250 omg fatal error")
         assert_equal Net::SMTPUnknownError, res.exception_class
       end
+
+      def test_smtp_exception_uses_standard_exception_message
+        error = Net::SMTPFatalError.new("original")
+        replacement = error.exception("replacement")
+
+        assert_equal "original", error.to_s
+        assert_equal "replacement", replacement.message
+      end
     end
   end
 end