diff --git a/aodndata/moorings/classifiers.py b/aodndata/moorings/classifiers.py
index 25896754..89639311 100644
--- a/aodndata/moorings/classifiers.py
+++ b/aodndata/moorings/classifiers.py
@@ -326,13 +326,18 @@ def dest_path(cls, input_file):
             dir_list += ['ASFS', 'SOFS', cat, 'Real-time', rt_folder_name]
         elif subfac in ('SOTS', 'ASFS'):
             dir_list.append('SOTS')
-            # Check for data_product_type attribute
-            if cls._get_nc_att(input_file, 'data_product_type'):
-                dir_list.append('derived_products')
-            else:
-                dir_list.append(cls._get_deployment_year(input_file))
-                if cls._is_realtime(input_file):
-                    dir_list.append('real-time')
+            # Open the NetCDF file
+            dataset = cls._open_nc_file(input_file)
+            try:
+                # Check for data_product_type attribute
+                if hasattr(dataset, 'data_product_type'):
+                    dir_list.append('derived_products')
+                else:
+                    dir_list.append(cls._get_deployment_year(input_file))
+                    if cls._is_realtime(input_file):
+                        dir_list.append('real-time')
+            finally:
+                dataset.close()
         else:
             raise InvalidFileNameError(
                 "Unknown DWM sub-facility '{subfac}' for file '{input_file}'".format(subfac=subfac,
diff --git a/test_aodndata/moorings/test_dwmFileClassifier.py b/test_aodndata/moorings/test_dwmFileClassifier.py
index 730d2a08..d0dd8e99 100644
--- a/test_aodndata/moorings/test_dwmFileClassifier.py
+++ b/test_aodndata/moorings/test_dwmFileClassifier.py
@@ -328,5 +328,19 @@ def test_hourly_depth_gridded_product(self):
         self.assertEqual(dest_dir, 'IMOS/DWM/DA/CSIRO_gridded_all_variables')
         self.assertEqual(dest_filename, filename)
 
+    def test_sots_derived_product(self):
+        filename = 'IMOS_DWM-SOTS_BCOPSTUW_20210420_SOFS_FV02_SOFS-10-2021-hourly-gridded-product_END-20220512_C-20221117.nc'
+        testfile = os.path.join(self.tempdir, filename)
+        make_test_file(testfile, {
+            'site_code': 'SOTS',
+            'platform_code': 'SOFS',
+            'data_product_type': 'derived'
+        })
+        dest_dir, dest_filename = os.path.split(DwmFileClassifier.dest_path(testfile))
+        expected_dir = 'IMOS/DWM/SOTS/derived_products'
+        self.assertEqual(dest_dir, expected_dir)
+        self.assertEqual(dest_filename, filename)
+
+
 if __name__ == '__main__':
     unittest.main()