diff --git a/intern/guardedalloc/intern/mallocn_intern.h b/intern/guardedalloc/intern/mallocn_intern.h
index 54acf7d6bd2..8a77a57b390 100644
--- a/intern/guardedalloc/intern/mallocn_intern.h
+++ b/intern/guardedalloc/intern/mallocn_intern.h
@@ -25,6 +25,8 @@
 #  define HAVE_MALLOC_STATS
 #elif defined(__FreeBSD__)
 #  include <malloc_np.h>
+#elif defined(__OpenBSD__)
+#  undef USE_MALLOC_USABLE_SIZE
 #elif defined(__APPLE__)
 #  include <malloc/malloc.h>
 #  define malloc_usable_size malloc_size