--- a/io/mmap.c
+++ b/io/mmap.c
@@ -189,7 +189,11 @@
 			prot |= PROT_EXEC;
 			break;
 		case 'S':
+ 			#ifdef MAP_SYNC
 			flags = MAP_SYNC | MAP_SHARED_VALIDATE;
+ 			#else
+ 			flags = MAP_SHARED_VALIDATE;
+ 			#endif
 
 			/*
 			 * If MAP_SYNC and MAP_SHARED_VALIDATE aren't defined
@@ -269,7 +273,11 @@
 	mapping->offset = offset;
 	mapping->name = filename;
 	mapping->prot = prot;
+ 	#ifdef MAP_SYNC
 	mapping->map_sync = (flags == (MAP_SYNC | MAP_SHARED_VALIDATE));
+ 	#else
+ 	mapping->map_sync = (flags == (MAP_SHARED_VALIDATE));
+ 	#endif
 	return 0;
 }