--- postfix-3.5.11/src/util/sys_defs.h~	2021-09-26 23:25:46.000000000 +0200
+++ postfix-3.5.11/src/util/sys_defs.h	2021-09-26 23:32:57.661271117 +0200
@@ -774,6 +774,7 @@
 #define PREPEND_PLUS_TO_OPTSTRING
 #define HAS_POSIX_REGEXP
 #define HAS_DLOPEN
+#define HAS_CLOSEFROM
 #define NATIVE_SENDMAIL_PATH "/usr/sbin/sendmail"
 #define NATIVE_MAILQ_PATH "/usr/bin/mailq"
 #define NATIVE_NEWALIAS_PATH "/usr/bin/newaliases"