diff --git a/tests/filters/test_gatefilter.py b/tests/filters/test_gatefilter.py
index dbe05133c2..854ef16adc 100644
--- a/tests/filters/test_gatefilter.py
+++ b/tests/filters/test_gatefilter.py
@@ -443,7 +443,7 @@ def test_moment_based_gate_filter():
     assert gfilter2.gate_excluded[0, -1] is np.True_
 
 
-sonde = netCDF4.Dataset(pyart.testing.SONDE_FILE, format="NETCDF4")
+sonde = netCDF4.Dataset(pyart.testing.SONDE_FILE, format="NETCDF4_CLASSIC")
 radar3 = pyart.io.read(pyart.testing.NEXRAD_ARCHIVE_MSG31_COMPRESSED_FILE)
 z_dict, temp_dict = pyart.retrieve.map_profile_to_gates(
     sonde.variables["tdry"][:], sonde.variables["alt"][:], radar3, toa=16500