diff --git a/lib/drb/ssl.rb b/lib/drb/ssl.rb
index 392d656..4e4d992 100644
--- a/lib/drb/ssl.rb
+++ b/lib/drb/ssl.rb
@@ -185,7 +185,7 @@ def setup_certificate
         }
 
         cert = OpenSSL::X509::Certificate.new
-        cert.version = 3
+        cert.version = 2
         cert.serial = 0
         name = OpenSSL::X509::Name.new(self[:SSLCertName])
         cert.subject = name