diff --git a/ortools/constraint_solver/routing_lp_scheduling.cc b/ortools/constraint_solver/routing_lp_scheduling.cc
index d65ed846a3..cc4cb95734 100644
--- a/ortools/constraint_solver/routing_lp_scheduling.cc
+++ b/ortools/constraint_solver/routing_lp_scheduling.cc
@@ -134,6 +134,9 @@ bool LocalDimensionCumulOptimizer::ComputePackedRouteCumuls(
       lp_solver_[vehicle].get(), packed_cumuls);
 }
 
+const int CumulBoundsPropagator::kNoParent = -2;
+const int CumulBoundsPropagator::kParentToBePropagated = -1;
+
 CumulBoundsPropagator::CumulBoundsPropagator(const RoutingDimension* dimension)
     : dimension_(*dimension), num_nodes_(2 * dimension->cumuls().size()) {
   outgoing_arcs_.resize(num_nodes_);
diff --git a/ortools/constraint_solver/routing_lp_scheduling.h b/ortools/constraint_solver/routing_lp_scheduling.h
index e7f5df7a7b..fbd21b4d55 100644
--- a/ortools/constraint_solver/routing_lp_scheduling.h
+++ b/ortools/constraint_solver/routing_lp_scheduling.h
@@ -47,8 +47,8 @@ class CumulBoundsPropagator {
     int head;
     int64 offset;
   };
-  static constexpr int kNoParent = -2;
-  static constexpr int kParentToBePropagated = -1;
+  static const int kNoParent;
+  static const int kParentToBePropagated;
 
   // Return the node corresponding to the lower bound of the cumul of index and
   // -index respectively.