diff --git a/Shorewall/Perl/Shorewall/Config.pm b/Shorewall/Perl/Shorewall/Config.pm
index 029afc813..80648b612 100644
--- a/Shorewall/Perl/Shorewall/Config.pm
+++ b/Shorewall/Perl/Shorewall/Config.pm
@@ -3273,7 +3273,7 @@ sub expand_variables( \$ ) {
 	    fatal_error "Variable Expansion Loop" if ++$count > 100;
 	}
 
-	$$lineref =~ s/??/@/g;
+	$$lineref =~ s/\?\?/@/g;
     }
 }