diff --git a/ProcessLib/BoundaryCondition/DirichletBoundaryConditionAuxiliaryFunctions.cpp b/ProcessLib/BoundaryCondition/DirichletBoundaryConditionAuxiliaryFunctions.cpp
index 928e1709c6a55a09f6eb2cd9ffa5bb843ab31be3..682e42dfa9e3d96903a71a88cb516a6744f4227b 100644
--- a/ProcessLib/BoundaryCondition/DirichletBoundaryConditionAuxiliaryFunctions.cpp
+++ b/ProcessLib/BoundaryCondition/DirichletBoundaryConditionAuxiliaryFunctions.cpp
@@ -70,8 +70,8 @@ void getEssentialBCValuesLocal(
     bc_values.values.clear();
 
     // convert mesh node ids to global index for the given component
-    bc_values.ids.reserve(bc_values.ids.size() + nodes_in_bc_mesh.size());
-    bc_values.values.reserve(bc_values.values.size() + nodes_in_bc_mesh.size());
+    bc_values.ids.reserve(nodes_in_bc_mesh.size());
+    bc_values.values.reserve(nodes_in_bc_mesh.size());
     for (auto const* const node : nodes_in_bc_mesh)
     {
         auto const id = node->getID();