diff --git a/src/problems/multi_region_problem.jl b/src/problems/multi_region_problem.jl
index 6bcbfbb..c251532 100644
--- a/src/problems/multi_region_problem.jl
+++ b/src/problems/multi_region_problem.jl
@@ -69,6 +69,10 @@ function instantiate_network_model(model::PSI.DecisionModel{MultiRegionProblem})
     return
 end
 
+function PSI.serialize_problem(model::PSI.DecisionModel{MultiRegionProblem};
+    optimizer::Nothing)
+end
+
 function PSI.build_model!(model::PSI.DecisionModel{MultiRegionProblem})
     build_impl!(
         PSI.get_optimization_container(model),