diff --git a/src/FEM/LagrangeSpace.hpp b/src/FEM/LagrangeSpace.hpp
index b1743cd4f..04d1e15fd 100644
--- a/src/FEM/LagrangeSpace.hpp
+++ b/src/FEM/LagrangeSpace.hpp
@@ -1417,7 +1417,7 @@ namespace ippl {
             });
         temp_field.accumulateHalo();
 
-        if ((bcType == PERIODIC_FACE) || (bcType == CONSTANT_FACE)) {
+        if (bcType == PERIODIC_FACE) {
             bcField.apply(temp_field);
             bcField.assignGhostToPhysical(temp_field);
         }
diff --git a/src/PoissonSolvers/FEMPoissonSolver.h b/src/PoissonSolvers/FEMPoissonSolver.h
index 8c183a6ea..6fd2a14ce 100644
--- a/src/PoissonSolvers/FEMPoissonSolver.h
+++ b/src/PoissonSolvers/FEMPoissonSolver.h
@@ -125,6 +125,11 @@ namespace ippl {
 
             // send boundary values to RHS (load vector) i.e. lifting (Dirichlet BCs)
             if (bcType == CONSTANT_FACE) {
+                // Set per-face Dirichlet values on physical boundary nodes before halo exchange;
+                // fillHalo must see the correct boundary state after load vector assembly.
+                bcField.apply(*(this->rhs_mp));
+                bcField.assignGhostToPhysical(*(this->rhs_mp));
+                this->rhs_mp->fillHalo();
                 *(this->rhs_mp) =
                     *(this->rhs_mp)
                     - lagrangeSpace_m.evaluateAx_lift(*(this->rhs_mp), poissonEquationEval);
diff --git a/src/PoissonSolvers/PreconditionedFEMPoissonSolver.h b/src/PoissonSolvers/PreconditionedFEMPoissonSolver.h
index 3b6c563ad..f0f4a5610 100644
--- a/src/PoissonSolvers/PreconditionedFEMPoissonSolver.h
+++ b/src/PoissonSolvers/PreconditionedFEMPoissonSolver.h
@@ -206,6 +206,11 @@ namespace ippl {
 
             // send boundary values to RHS (load vector) i.e. lifting (Dirichlet BCs)
             if (bcType == CONSTANT_FACE) {
+                // Set per-face Dirichlet values on physical boundary nodes before halo exchange;
+                // fillHalo must see the correct boundary state after load vector assembly.
+                bcField.apply(*(this->rhs_mp));
+                bcField.assignGhostToPhysical(*(this->rhs_mp));
+                this->rhs_mp->fillHalo();
                 *(this->rhs_mp) =
                     *(this->rhs_mp)
                     - lagrangeSpace_m.evaluateAx_lift(*(this->rhs_mp), poissonEquationEval);