diff --git a/src/services_models/service_slacks.jl b/src/services_models/service_slacks.jl
index 0ec2464fd..9d530e3e4 100644
--- a/src/services_models/service_slacks.jl
+++ b/src/services_models/service_slacks.jl
@@ -1,7 +1,7 @@
 function reserve_slacks!(
     container::OptimizationContainer,
     service::T,
-) where {T <: PSY.Reserve}
+) where {T <: Union{PSY.Reserve, PSY.ReserveNonSpinning}}
     time_steps = get_time_steps(container)
     variable = add_variable_container!(
         container,