diff --git a/git-send-email.perl b/git-send-email.perl
index 2a3873b744..6caa5b563f 100755
--- a/git-send-email.perl
+++ b/git-send-email.perl
@@ -1332,6 +1332,13 @@ Message-Id: $message_id
 			require Net::SMTP::SSL;
 			$smtp_domain ||= maildomain();
 			require IO::Socket::SSL;
+
+			# Suppress "variable accessed once" warning.
+			{
+				no warnings 'once';
+				$IO::Socket::SSL::DEBUG = 1;
+			}
+
 			# Net::SMTP::SSL->new() does not forward any SSL options
 			IO::Socket::SSL::set_client_defaults(
 				ssl_verify_params());