diff --git a/mpas_analysis/ocean/compute_transects_subtask.py b/mpas_analysis/ocean/compute_transects_subtask.py
index b4b8ab0db..e224dc104 100644
--- a/mpas_analysis/ocean/compute_transects_subtask.py
+++ b/mpas_analysis/ocean/compute_transects_subtask.py
@@ -586,7 +586,7 @@ def _compute_mpas_transects(self, dsMesh):
                 # reads them back because of _FillValue
                 dsMpasTransect.to_netcdf(transectInfoFileName)
 
-                dsTransectOnMpas = xr.Dataset(dsMpasTransect)
+                dsTransectOnMpas = dsMpasTransect.copy()
                 dsTransectOnMpas['x'] = dsMpasTransect.dNode
 
                 dsTransectOnMpas['z'] = dsMpasTransect.zTransectNode
@@ -608,7 +608,7 @@ def _compute_mpas_transects(self, dsMesh):
             for season in self.seasons:
                 maskedFileName = self.get_masked_file_name(season)
                 with xr.open_dataset(maskedFileName) as dsMask:
-                    dsOnMpas = xr.Dataset(dsMpasTransect)
+                    dsOnMpas = dsMpasTransect.copy()
                     for var in dsMask.data_vars:
                         dims = dsMask[var].dims
                         if 'nCells' in dims and (