--- lib/vmalloc/vmhdr.h.orig	2019-09-12 02:11:30 UTC
+++ lib/vmalloc/vmhdr.h
@@ -20,6 +20,10 @@ extern "C" {
 #ifndef _BLD_vmalloc
 #define _BLD_vmalloc	1
 #endif
+#if defined(__FreeBSD__) && (defined(__aarch64__) || defined(__riscv))
+/* No sbrk on FreeBSD/AArch64 or FreeBSD/RISC-V */
+#define _BLD_INSTRUMENT	1
+#endif
 #ifdef _WIN32
 #include <io.h>
 #endif