diff --git a/util/TLSProxy/ClientHello.pm b/util/TLSProxy/ClientHello.pm
index 383062842c8da49b1b50631144af097bf50b61a7..0586cf9a54affffde1c2fc4096bbbda8371c1b21 100644
--- a/util/TLSProxy/ClientHello.pm
+++ b/util/TLSProxy/ClientHello.pm
@@ -55,7 +55,8 @@ use strict;
 
 package TLSProxy::ClientHello;
 
-use parent 'TLSProxy::Message';
+use vars '@ISA';
+push @ISA, 'TLSProxy::Message';
 
 sub new
 {
diff --git a/util/TLSProxy/NewSessionTicket.pm b/util/TLSProxy/NewSessionTicket.pm
index 75dbf232340b44a0662ea4e0a38de62f6582787c..4e8c71381147f0f832d0ec011472e970f53c4a15 100644
--- a/util/TLSProxy/NewSessionTicket.pm
+++ b/util/TLSProxy/NewSessionTicket.pm
@@ -54,7 +54,8 @@ use strict;
 
 package TLSProxy::NewSessionTicket;
 
-use parent 'TLSProxy::Message';
+use vars '@ISA';
+push @ISA, 'TLSProxy::Message';
 
 sub new
 {
diff --git a/util/TLSProxy/ServerHello.pm b/util/TLSProxy/ServerHello.pm
index 7cf753508d1dda62473ddb8a2a0e9309fb8ff87a..4798f2214051ec5448820d442b23df9049e4faf4 100644
--- a/util/TLSProxy/ServerHello.pm
+++ b/util/TLSProxy/ServerHello.pm
@@ -55,7 +55,8 @@ use strict;
 
 package TLSProxy::ServerHello;
 
-use parent 'TLSProxy::Message';
+use vars '@ISA';
+push @ISA, 'TLSProxy::Message';
 
 sub new
 {
diff --git a/util/TLSProxy/ServerKeyExchange.pm b/util/TLSProxy/ServerKeyExchange.pm
index b85b8addca833f4e16afec7936601b945eb18eec..a3973be96298c87b40e515c7e9a5d81cdcf038db 100644
--- a/util/TLSProxy/ServerKeyExchange.pm
+++ b/util/TLSProxy/ServerKeyExchange.pm
@@ -55,7 +55,8 @@ use strict;
 
 package TLSProxy::ServerKeyExchange;
 
-use parent 'TLSProxy::Message';
+use vars '@ISA';
+push @ISA, 'TLSProxy::Message';
 
 sub new
 {
diff --git a/util/dofile.pl b/util/dofile.pl
index 76dfe2b607f44f011c0a490a1554a6b8c2c07f99..78b8dfed9d4ac8bd16ffff53e7df9a585bdb3e2f 100644
--- a/util/dofile.pl
+++ b/util/dofile.pl
@@ -35,7 +35,9 @@ use File::Spec::Functions;
 use lib catdir(dirname(__FILE__));
 use with_fallback qw(Text::Template);
 
-use parent qw/Text::Template/;
+#use parent qw/Text::Template/;
+use vars qw/@ISA/;
+push @ISA, qw/Text::Template/;
 
 # Override constructor
 sub new {