diff --git a/mps/manual/source/topic/arena.rst b/mps/manual/source/topic/arena.rst
index a309a950ac8..28fe9e0cad8 100644
--- a/mps/manual/source/topic/arena.rst
+++ b/mps/manual/source/topic/arena.rst
@@ -279,7 +279,7 @@ Virtual memory arenas
       that's smaller than the operating system page size, the MPS
       rounds it up to the page size and continues.
 
-    A second optional :term:`keyword argument` may be passed, but it
+    A third optional :term:`keyword argument` may be passed, but it
     only has any effect on the Windows operating system:
 
     * :c:macro:`MPS_KEY_VMW3_TOP_DOWN` (type :c:type:`mps_bool_t`). If