diff --git a/compliance_checker/cf/cf_1_6.py b/compliance_checker/cf/cf_1_6.py
index 2bf0f74a..c1280d96 100644
--- a/compliance_checker/cf/cf_1_6.py
+++ b/compliance_checker/cf/cf_1_6.py
@@ -3340,7 +3340,7 @@ def check_packed_data(self, ds):
 
             # IMPLEMENTATION CONFORMANCE 8.1 REQUIRED 1/3
             # scale_factor and add_offset same type
-            if type(add_offset) != type(scale_factor):
+            if not isinstance(add_offset, type(scale_factor)):
                 valid = False
                 reasoning.append(
                     "Attributes add_offset and scale_factor have different data type.",
@@ -3350,7 +3350,7 @@ def check_packed_data(self, ds):
             # if not the same type
             # FIXME: Check add_offset too.
 
-            elif type(scale_factor) != var.dtype.type:
+            elif not isinstance(scale_factor, var.dtype.type):
                 # Check both attributes are type float or double
                 if not isinstance(scale_factor, (float, np.floating)):
                     valid = False
diff --git a/compliance_checker/cf/cf_1_9.py b/compliance_checker/cf/cf_1_9.py
index 73211e44..3fcf5dfe 100644
--- a/compliance_checker/cf/cf_1_9.py
+++ b/compliance_checker/cf/cf_1_9.py
@@ -150,7 +150,10 @@ def check_domain_variables(self, ds: Dataset):
                     continue
                 appendix_a_not_recommended_attrs = []
                 for attr_name in domain_var.ncattrs():
-                    if attr_name in self.appendix_a and "D" not in self.appendix_a[attr_name]["attr_loc"]:
+                    if (
+                        attr_name in self.appendix_a
+                        and "D" not in self.appendix_a[attr_name]["attr_loc"]
+                    ):
                         appendix_a_not_recommended_attrs.append(attr_name)
 
                 if appendix_a_not_recommended_attrs:
@@ -163,10 +166,12 @@ def check_domain_variables(self, ds: Dataset):
                 # no errors occurred
                 domain_valid.score += 1
 
-
             # IMPLEMENTATION CONFORMANCE 5.8 REQUIRED 4/4
             if hasattr(domain_var, "cell_measures"):
-                cell_measures_var_names = regex.findall(r"\b(?:area|volume):\s+(\w+)", domain_var.cell_measures)
+                cell_measures_var_names = regex.findall(
+                    r"\b(?:area|volume):\s+(\w+)",
+                    domain_var.cell_measures,
+                )
                 # check exist
                 for var_name in cell_measures_var_names:
                     try:
@@ -174,10 +179,16 @@ def check_domain_variables(self, ds: Dataset):
                     except ValueError:
                         # TODO: what to do here?
                         continue
-                    domain_coord_var_names = {var_like.name for var_like in domain_coord_vars}
-                    domain_valid.assert_true(set(cell_measures_variable.dimensions).issubset(domain_coord_var_names),
-                                             "Variables named in the cell_measures attributes must have a dimensions attribute with "
-                                             "values that are a subset of the referring domain variable's dimension attribute")
+                    domain_coord_var_names = {
+                        var_like.name for var_like in domain_coord_vars
+                    }
+                    domain_valid.assert_true(
+                        set(cell_measures_variable.dimensions).issubset(
+                            domain_coord_var_names,
+                        ),
+                        "Variables named in the cell_measures attributes must have a dimensions attribute with "
+                        "values that are a subset of the referring domain variable's dimension attribute",
+                    )
 
             results.append(domain_valid.to_result())
 
diff --git a/compliance_checker/tests/test_cf.py b/compliance_checker/tests/test_cf.py
index f053f837..65088f84 100644
--- a/compliance_checker/tests/test_cf.py
+++ b/compliance_checker/tests/test_cf.py
@@ -3249,7 +3249,7 @@ def test_domain(self):
         dataset.createDimension("lat", 20)
         dataset.createDimension("depth", 20)
         domain_var.setncattr("dimensions", "lon lat depth")
-        cube = dataset.createVariable("cube", "f8", ("lon", "lat", "depth"))
+        dataset.createVariable("cube", "f8", ("lon", "lat", "depth"))
         # OK, coordinates in cell_measures are subset of coordinates of
         # referring domain variable's coordinates attribute
         results = self.cf.check_domain_variables(dataset)
@@ -3258,10 +3258,12 @@ def test_domain(self):
         domain_var.cell_measures = "volume: cube_bad"
         dataset.createVariable("cube_bad", "f8", ("lon", "lat", "depth", "time"))
         results = self.cf.check_domain_variables(dataset)
-        self.assertTrue("Variables named in the cell_measures attributes must "
-                        "have a dimensions attribute with values that are a "
-                        "subset of the referring domain variable's dimension "
-                        "attribute" in results[0].msgs)
+        self.assertTrue(
+            "Variables named in the cell_measures attributes must "
+            "have a dimensions attribute with values that are a "
+            "subset of the referring domain variable's dimension "
+            "attribute" in results[0].msgs,
+        )
         del dataset
         dataset = MockTimeSeries()
         # domain should be dimensionless -- currently not an error in