diff --git a/exercises/standard_library_types/arc1.rs b/exercises/standard_library_types/arc1.rs
index fe33803..e6c220b 100644
--- a/exercises/standard_library_types/arc1.rs
+++ b/exercises/standard_library_types/arc1.rs
@@ -7,7 +7,7 @@
 // The second thread (offset 1), will sum 1, 9, 17, ...
 // The third thread (offset 2), will sum 2, 10, 18, ...
 // ...
-// The eighth thread {offset 7}, will sum 7, 15, 23, ...
+// The eighth thread (offset 7), will sum 7, 15, 23, ...
 
 // Because we are using threads, our values need to be thread-safe.  Therefore,
 // we are using Arc.  We need to make a change in each of the two TODOs.