diff --git a/compiler.rst b/compiler.rst
--- a/compiler.rst
+++ b/compiler.rst
@@ -169,7 +169,7 @@
 In general, unless you are working on the critical core of the compiler, memory
 management can be completely ignored.  But if you are working at either the
 very beginning of the compiler or the end, you need to care about how the arena
-works.  All code relating to the arena is in either Include/pyarena.h or
+works.  All code relating to the arena is either in Include/pyarena.h or in
 Python/pyarena.c .
 
 PyArena_New() will create a new arena.  The returned PyArena structure will