diff --git a/src/input4mips_validation/validation/comment.py b/src/input4mips_validation/validation/comment.py
index 0cfc77b8..9c5da385 100644
--- a/src/input4mips_validation/validation/comment.py
+++ b/src/input4mips_validation/validation/comment.py
@@ -20,5 +20,7 @@ def validate_comment(comment: str) -> None:
         `comment`'s value is not a string
     """
     if not isinstance(comment, str):
-        msg = f"The `comment` attribute must be a string, received {comment=!r}."
+        msg = (  # type: ignore[unreachable]
+            f"The `comment` attribute must be a string, received {comment=!r}."
+        )
         raise TypeError(msg)
diff --git a/src/input4mips_validation/validation/datasets_to_write_to_disk.py b/src/input4mips_validation/validation/datasets_to_write_to_disk.py
index 9dfa9faf..a11934ae 100644
--- a/src/input4mips_validation/validation/datasets_to_write_to_disk.py
+++ b/src/input4mips_validation/validation/datasets_to_write_to_disk.py
@@ -183,16 +183,10 @@ def get_ds_to_write_to_disk_validation_result(
         vrs = ValidationResultsStore()
 
     # Metadata that can be validated standalone
-    verification_standalone_l = [
+    verification_standalone = (
         ("creation_date", validate_creation_date),
         ("tracking_id", validate_tracking_id),
-    ]
-    # Optional attributes
-    for optional_attr, verification_func in (("comment", validate_comment),):
-        if optional_attr in ds.attrs:
-            verification_standalone_l.append((optional_attr, verification_func))
-
-    verification_standalone = tuple(verification_standalone_l)
+    )
 
     # Metadata that depends on the data
     ds_variables = xr_variable_processor.get_ds_variables(
@@ -227,6 +221,16 @@ def get_ds_to_write_to_disk_validation_result(
             func_description=f"Validate the {attribute!r} attribute",
         )(ds, attribute, validation_function)
 
+    # Optional attributes
+    for attribute_optional, validation_function_optional in (
+        ("comment", validate_comment),
+    ):
+        if attribute_optional in ds.attrs:
+            vrs.wrap(
+                validate_attribute,
+                func_description=f"Validate the {attribute_optional!r} attribute",
+            )(ds, attribute_optional, validation_function_optional)
+
     # Metadata that is defined by the combination of other metadata and the CVs
     verification_defined_by_cvs_and_other_metadata = (
         (