diff --git a/freebsd/sys/vm/uma_core.c b/freebsd/sys/vm/uma_core.c
index 845c4339..7badb362 100644
--- a/freebsd/sys/vm/uma_core.c
+++ b/freebsd/sys/vm/uma_core.c
@@ -98,7 +98,7 @@ __FBSDID("$FreeBSD$");
     #undef curcpu
     #define curcpu rtems_get_current_processor()
     #undef mp_maxid
-    #define mp_maxid rtems_get_processor_count()
+    #define mp_maxid (rtems_get_processor_count() - 1)
     #define SMP
   #endif
 #endif /* __rtems__ */