diff --git a/mpas_analysis/shared/mpas_xarray/mpas_xarray.py b/mpas_analysis/shared/mpas_xarray/mpas_xarray.py
index a95ce2ce5..c2c17771c 100644
--- a/mpas_analysis/shared/mpas_xarray/mpas_xarray.py
+++ b/mpas_analysis/shared/mpas_xarray/mpas_xarray.py
@@ -153,7 +153,8 @@ def get_datetimes(time_var, yearoffset):  # {{{
         datetimes = [start + x for x in
                      pd.to_timedelta(time_var.values, unit='ns')]
     else:
-        raise TypeError("time_var of unsupported type")
+        raise TypeError("time_var of unsupported type {}".format(
+            time_var.dtype))
 
     return datetimes  # }}}