diff --git a/model/task/concept.v b/model/task/concept.v
index 93727169fdb0bb72e44c7cad64d68482d1457325..5b8a0e5ca45e79222c1adb9cbc57ac6f2f0f2280 100644
--- a/model/task/concept.v
+++ b/model/task/concept.v
@@ -72,7 +72,7 @@ Section ModelValidity.
     Definition valid_job_cost j :=
       job_cost j <= task_cost (job_task j).
 
-    (** Every job have a valid job cost *)
+    (** Every job has a valid job cost. *)
     Definition jobs_have_valid_job_costs :=
       forall j, valid_job_cost j.