diff --git a/Source/BoundaryConditions/PML.cpp b/Source/BoundaryConditions/PML.cpp
index 8cc18d93cda..449e4ba2c84 100644
--- a/Source/BoundaryConditions/PML.cpp
+++ b/Source/BoundaryConditions/PML.cpp
@@ -776,12 +776,14 @@ PML::PML (const int lev, const BoxArray& grid_ba, const DistributionMapping& gri
                     if (do_pml_Lo[idim]) {
                         Box const& bb = amrex::adjCellLo(b, idim);
                         if ( ! grid_cba.intersects(bb) ) {
+                            WARPX_ALWAYS_ASSERT_WITH_MESSAGE(b.length(idim) > ncell/ref_ratio[idim], " box length must be greater that pml size");
                             b.growLo(idim, -ncell/ref_ratio[idim]);
                         }
                     }
                     if (do_pml_Hi[idim]) {
                         Box const& bb = amrex::adjCellHi(b, idim);
                         if ( ! grid_cba.intersects(bb) ) {
+                            WARPX_ALWAYS_ASSERT_WITH_MESSAGE(b.length(idim) > ncell/ref_ratio[idim], " box length must be greater that pml size");
                             b.growHi(idim, -ncell/ref_ratio[idim]);
                         }
                     }