diff --git a/README.md b/README.md
index 5b88fc1..26d036d 100644
--- a/README.md
+++ b/README.md
@@ -29,10 +29,10 @@ certain design goals.
   that it will not (and indeed cannot) mutate the supplied entity. Similarly, a
   read-only interface can be returned to a private internal field without fear
   that the recipient will mutate it and wreak havoc. Note that the interfaces
-  have a very small, but non-zero performance cost versus direct use of the
-  mutable classes. So use the interfaces anyway and then profile your
-  application to determine whether there are places where you need to sacrifice
-  code clarity and safety on the altar of higher performance.
+  have a very small, but non-zero, performance cost versus direct use of the
+  mutable classes. Use the interfaces anyway and then profile your application
+  to determine whether there are places where you need to sacrifice code
+  clarity and safety on the altar of higher performance.
 
 * The library supports garbage creation avoidance (for applications which are
   sensitive to garbage collection pauses, like video games). For example, in