diff --git a/message_ix/model/MESSAGE/model_core.gms b/message_ix/model/MESSAGE/model_core.gms
index e549c7fb1..8fcb836e6 100644
--- a/message_ix/model/MESSAGE/model_core.gms
+++ b/message_ix/model/MESSAGE/model_core.gms
@@ -687,7 +687,7 @@ CAPACITY_CONSTRAINT(node,inv_tec,vintage,year,time)$( map_tec_time(node,inv_tec,
 *
 * Equation CAPACITY_MAINTENANCE_HIST
 * """"""""""""""""""""""""""""""""""
-* The following three constraints implement technology capacity maintenance over time to allow early retirment.
+* The following three constraints implement technology capacity maintenance over time to allow early retirement.
 * The optimization problem determines the optimal timing of retirement, when fixed operation-and-maintenance costs
 * exceed the benefit in the objective function.
 *