diff --git a/src/s/sunos413.h b/src/s/sunos413.h
index 3caae6e7378..5dedb2947f6 100644
--- a/src/s/sunos413.h
+++ b/src/s/sunos413.h
@@ -9,3 +9,5 @@
 #ifndef SYSTEM_MALLOC
 #define MEMMOVE_MISSING
 #endif
+
+#define USE_MMAP_FOR_BUFFERS 1