diff --git a/sys/sys/cdefs.h b/sys/sys/cdefs.h
--- a/sys/sys/cdefs.h
+++ b/sys/sys/cdefs.h
@@ -720,6 +720,20 @@
 #define	__POSIX_VISIBLE		198808
 #define	__ISO_C_VISIBLE		0
 #endif /* _POSIX_C_SOURCE */
+
+/*
+ * Sun defined a large filesystem interface. If the user requested it, provide
+ * a way for headers to ask for it.
+ * _FILE_OFFSET_BITS is handled elsewhere since it doesn't fit nicely into the
+ * visible paradigm, and FreeBSD acts as if it were always defined to be 64
+ * and cannot support a value of 32.
+ */
+#ifdef _LARGEFILE64_SOURCE
+#define	__LFS_VISIBLE		1
+#else
+#define	__LFS_VISIBLE		0
+#endif
+
 /*
  * Both glibc and OpenBSD enable c11 features when _ISOC11_SOURCE is defined, or
  * when compiling with -stdc=c11. A strict reading of the standard would suggest