diff --git a/src/ch17-05-traits-for-async.md b/src/ch17-05-traits-for-async.md
index 4b502ceafe..7f2b66bd4d 100644
--- a/src/ch17-05-traits-for-async.md
+++ b/src/ch17-05-traits-for-async.md
@@ -131,7 +131,7 @@ yet ready.
 
 Back in Listing 17-13, we used the `trpl::join!` macro to await three
 futures. However, it’s common to have a collection such as a vector containing
-some number futures that won’t be known until runtime. Let’s change Listing
+some number of futures that won’t be known until runtime. Let’s change Listing
 17-13 to the code in Listing 17-23 that puts the three futures into a vector
 and calls the `trpl::join_all` function instead, which won’t compile yet.