diff --git a/servers/vm/vm.h b/servers/vm/vm.h
index e8eaade38..89af44569 100644
--- a/servers/vm/vm.h
+++ b/servers/vm/vm.h
@@ -22,6 +22,7 @@
 #define VMSTATS		0
 
 /* VM behaviour */
+#define MEMPROTECT	0	/* Slab objects not mapped. Access with USE() */
 #define JUNKFREE	0	/* Fill freed pages with junk */
 #define NONCONTIGUOUS	0	/* Make phys pages max. noncontiguous */