--- opensmtpd-6.0.2p1/openbsd-compat/defines.h
+++ opensmtpd-6.0.2p1-patched/openbsd-compat/defines.h
@@ -85,7 +85,7 @@
 # define STDERR_FILENO   2
 #endif
 
-#if defined(HAVE_DECL_O_NONBLOCK) && HAVE_DECL_O_NONBLOCK == 0
+#if !HAVE_DECL_O_NONBLOCK
 # define O_NONBLOCK      00004	/* Non Blocking Open */
 #endif
 
--- opensmtpd-6.0.2p1/openbsd-compat/openbsd-compat.h
+++ opensmtpd-6.0.2p1-patched/openbsd-compat/openbsd-compat.h
@@ -212,11 +212,11 @@
 #define pledge(promises, paths) 0
 #endif
 
-#ifndef HAVE_DECL_AF_LOCAL
+#if !HAVE_DECL_AF_LOCAL
 #define AF_LOCAL AF_UNIX
 #endif
 
-#ifndef HAVE_DECL_WAIT_MYPGRP
+#if !HAVE_DECL_WAIT_MYPGRP
 #define WAIT_MYPGRP 0
 #endif
 
--- opensmtpd-6.0.2p1/smtpd/to.c
+++ opensmtpd-6.0.2p1-patched/smtpd/to.c
@@ -210,7 +210,7 @@
 #if HAVE_STRUCT_TM_TM_GMTOFF
 	offset = lt->tm_gmtoff;
 	tz = lt->tm_zone;
-#elif defined HAVE_DECL_ALTZONE && defined HAVE_DECL_TIMEZONE
+#elif HAVE_DECL_ALTZONE && HAVE_DECL_TIMEZONE
 	offset = lt->tm_isdst > 0 ? altzone : timezone;
 	tz = lt->tm_isdst > 0 ? tzname[1] : tzname[0];
 #endif