diff --git a/dev-ruby/net-smtp/net-smtp-0.5.1.ebuild b/dev-ruby/net-smtp/net-smtp-0.5.1.ebuild
index bc388bb3a021..a31b7855bc0b 100644
--- a/dev-ruby/net-smtp/net-smtp-0.5.1.ebuild
+++ b/dev-ruby/net-smtp/net-smtp-0.5.1.ebuild
@@ -2,7 +2,8 @@
 # Distributed under the terms of the GNU General Public License v2
 
 EAPI=8
-USE_RUBY="ruby31 ruby32 ruby33 ruby34"
+
+USE_RUBY="ruby32 ruby33 ruby34 ruby40"
 
 RUBY_FAKEGEM_BINWRAP=""
 RUBY_FAKEGEM_EXTRADOC="NEWS.md README.md"