diff --git a/modules/lib/Mail/MIMEDefang.pm b/modules/lib/Mail/MIMEDefang.pm
index e202281..162c542 100644
--- a/modules/lib/Mail/MIMEDefang.pm
+++ b/modules/lib/Mail/MIMEDefang.pm
@@ -38,6 +38,7 @@ no warnings qw(once uninitialized);
 require Exporter;
 
 use Carp;
+use Socket;
 use Errno qw(ENOENT EACCES);
 use File::Spec;
 use MIME::Entity;