diff --git a/Src/Particle/AMReX_NeighborParticlesGPUImpl.H b/Src/Particle/AMReX_NeighborParticlesGPUImpl.H
index 6e112318757..81bef1302e2 100644
--- a/Src/Particle/AMReX_NeighborParticlesGPUImpl.H
+++ b/Src/Particle/AMReX_NeighborParticlesGPUImpl.H
@@ -121,7 +121,7 @@ buildNeighborCopyOp (bool use_boundary_neighbor)
 {
     BL_PROFILE("NeighborParticleContainer<NStructReal, NStructInt, NArrayReal, NArrayInt>::buildNeighborCopyOp()");
 
-    AMREX_ASSERT(hasNeighbors() == false);
+    AMREX_ASSERT(!hasNeighbors() || use_boundary_neighbor);
 
     const int lev = 0;
     const auto& geom = this->Geom(lev);
diff --git a/Src/Particle/AMReX_NeighborParticlesI.H b/Src/Particle/AMReX_NeighborParticlesI.H
index fc5788145b7..e0c4c066a75 100644
--- a/Src/Particle/AMReX_NeighborParticlesI.H
+++ b/Src/Particle/AMReX_NeighborParticlesI.H
@@ -857,8 +857,8 @@ selectActualNeighbors (CheckPair&& check_pair, int num_cells)
             auto pperm   = bins.permutationPtr();
             auto poffset = bins.offsetsPtr();
 
-            unsigned int  np_boundary    = 0;
-            unsigned int* p_np_boundary  = &np_boundary;
+            Gpu::Buffer<unsigned int> np_boundary({0});
+            unsigned int* p_np_boundary = np_boundary.data();
             constexpr unsigned int max_unsigned_int = std::numeric_limits<unsigned int>::max();
 
             AMREX_FOR_1D ( np_real, i,
@@ -899,9 +899,9 @@ selectActualNeighbors (CheckPair&& check_pair, int num_cells)
                     }
                 }
             });// end amrex_for_1d
-            Gpu::streamSynchronize();
 
-            m_boundary_particle_ids[lev][index].resize(np_boundary);
+            unsigned int* p_np_boundary_h = np_boundary.copyToHost();
+            m_boundary_particle_ids[lev][index].resize(*p_np_boundary_h);
 
         }// end mypariter
     }// end lev