diff --git a/exercises/standard_library_types/arc1.rs b/exercises/standard_library_types/arc1.rs
index f90ae74..fe33803 100644
--- a/exercises/standard_library_types/arc1.rs
+++ b/exercises/standard_library_types/arc1.rs
@@ -5,7 +5,7 @@
 // Each thread is going to get the sum of every eighth value, with an offset.
 // The first thread (offset 0), will sum 0, 8, 16, ...
 // The second thread (offset 1), will sum 1, 9, 17, ...
-// The third thread (offset 2}, will sum 2, 10, 18, ...
+// The third thread (offset 2), will sum 2, 10, 18, ...
 // ...
 // The eighth thread {offset 7}, will sum 7, 15, 23, ...