diff --git a/src/netcdf/netcdf.f90 b/src/netcdf/netcdf.f90
index 04ba92bc0..a197ac944 100644
--- a/src/netcdf/netcdf.f90
+++ b/src/netcdf/netcdf.f90
@@ -348,10 +348,10 @@ module function netcdf_read_frame_base(self, iu, param) result(ierr)
             select type(self)
             class is (swiftest_pl)
                ind(:) = pack(ind(:), (.not.tpmask(:) .and. validmask(:)))
-               n = count(.not.tpmask(:))
+               n = count(.not.tpmask(:) .and. validmask(:))
             class is (swiftest_tp)
                ind(:) = pack(ind(:), (tpmask(:) .and. validmask(:)))
-               n = count(tpmask(:))
+               n = count(tpmask(:) .and. validmask(:))
             end select
 
             do i = j, n