diff --git a/Shorewall/Perl/Shorewall/Config.pm b/Shorewall/Perl/Shorewall/Config.pm
index 5a4fdd6a1..4f3b6572f 100644
--- a/Shorewall/Perl/Shorewall/Config.pm
+++ b/Shorewall/Perl/Shorewall/Config.pm
@@ -685,6 +685,7 @@ sub initialize( $ ) {
 	       FLOW_FILTER => undef,
 	       FWMARK_RT_MASK => undef,
 	       MARK_ANYWHERE => undef,
+	       HEADER_MATCH => undef,
 	       CAPVERSION => undef,
 	       KERNELVERSION => undef,
 	       );