diff --git a/gnu/usr.bin/man/man/man.c b/gnu/usr.bin/man/man/man.c
index 72a9fd589ae4..88efe85adf0b 100644
--- a/gnu/usr.bin/man/man/man.c
+++ b/gnu/usr.bin/man/man/man.c
@@ -31,7 +31,7 @@
 #include "gripes.h"
 #include "version.h"
 
-#ifndef POSIX
+#ifdef POSIX
 #include <unistd.h>
 #else
 #ifndef R_OK