diff --git a/libc/include/limits.h b/libc/include/limits.h
index 69df082..6ae629b 100644
--- a/libc/include/limits.h
+++ b/libc/include/limits.h
@@ -97,4 +97,5 @@
 /* POSIX says these belong in <unistd.h> but BSD has some in <limits.h>. */
 #include <machine/posix_limits.h>
 
+#define HOST_NAME_MAX _POSIX_HOST_NAME_MAX
 #endif /* !_LIMITS_H_ */