diff --git a/lib/iris/fileformats/netcdf.py b/lib/iris/fileformats/netcdf.py
index 4d7ddedc61..6f17f6cd9d 100644
--- a/lib/iris/fileformats/netcdf.py
+++ b/lib/iris/fileformats/netcdf.py
@@ -22,6 +22,7 @@
 import warnings
 
 import dask.array as da
+import cf_units
 import netCDF4
 import numpy as np
 import numpy.ma as ma
@@ -1760,7 +1761,7 @@ def _inner_create_cf_cellmeasure_or_ancil_variable(
         # Add the data to the CF-netCDF variable.
         cf_var[:] = data
 
-        if dimensional_metadata.units != "unknown":
+        if dimensional_metadata.units.is_udunits():
             _setncattr(cf_var, "units", str(dimensional_metadata.units))
 
         if dimensional_metadata.standard_name is not None:
@@ -1926,7 +1927,7 @@ def _create_cf_coord_variable(self, cube, dimension_names, coord):
         # Deal with CF-netCDF units and standard name.
         standard_name, long_name, units = self._cf_coord_identity(coord)
 
-        if units != "unknown":
+        if cf_units.as_unit(units).is_udunits():
             _setncattr(cf_var, "units", units)
 
         if standard_name is not None:
@@ -2371,7 +2372,7 @@ def store(data, cf_var, fill_value):
         if cube.long_name:
             _setncattr(cf_var, "long_name", cube.long_name)
 
-        if cube.units != "unknown":
+        if cube.units.is_udunits():
             _setncattr(cf_var, "units", str(cube.units))
 
         # Add the CF-netCDF calendar attribute.
diff --git a/lib/iris/tests/results/netcdf/netcdf_save_no_name.cdl b/lib/iris/tests/results/netcdf/netcdf_save_no_name.cdl
index e67316b2f7..e01eb1b31a 100644
--- a/lib/iris/tests/results/netcdf/netcdf_save_no_name.cdl
+++ b/lib/iris/tests/results/netcdf/netcdf_save_no_name.cdl
@@ -10,7 +10,6 @@ variables:
 	double dim1(dim1) ;
 		dim1:units = "m" ;
 	char unknown_scalar(string6) ;
-		unknown_scalar:units = "no_unit" ;
 
 // global attributes:
 		:Conventions = "CF-1.7" ;