Index: head/graphics/graphviz/files/patch-lib-vmalloc-vmhdr.h
===================================================================
--- head/graphics/graphviz/files/patch-lib-vmalloc-vmhdr.h	(revision 564077)
+++ head/graphics/graphviz/files/patch-lib-vmalloc-vmhdr.h	(revision 564078)
@@ -1,13 +1,13 @@
 --- 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__)
-+/* No sbrk on FreeBSD/AArch64 */
++#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