diff --git a/src/chexus/validators.py b/src/chexus/validators.py
index 96c4f22..210c732 100644
--- a/src/chexus/validators.py
+++ b/src/chexus/validators.py
@@ -307,14 +307,13 @@ def validate(self, node: Dataset | Group) -> Violation | None:
         return Violation(node.name)
 
 
-class detector_numbers_unique_in_all_detectors(Validator):
+class detector_numbers_unique_in_detector(Validator):
     def __init__(self) -> None:
         super().__init__(
             "detector_numbers are not unique",
             "The values in all detector_numbers fields in all "
             "detectors should be unique.",
         )
-        self._seen_detector_numbers = np.array([], dtype='int')
 
     def applies_to(self, node: Dataset | Group) -> bool:
         return (
@@ -324,14 +323,11 @@ def applies_to(self, node: Dataset | Group) -> bool:
         )
 
     def validate(self, node: Dataset | Group) -> Violation | None:
-        detector_numbers = np.asarray(node.children['detector_number'].value).ravel()
+        detector_numbers = np.asarray(node.children['detector_number'].value)
         if not hasattr(detector_numbers, '__len__'):
             return
-        if np.isin(detector_numbers, self._seen_detector_numbers).any():
+        if not len(detector_numbers.ravel()) == len(np.unique(detector_numbers)):
             return Violation(node.name)
-        self._seen_detector_numbers = np.concatenate(
-            (self._seen_detector_numbers, detector_numbers)
-        )
 
 
 class event_id_subset_of_detector_number(Validator):
@@ -480,7 +476,7 @@ def base_validators(*, has_scipp=True):
         transformation_offset_units_missing(),
         units_invalid(),
         NXlog_has_value(),
-        detector_numbers_unique_in_all_detectors(),
+        detector_numbers_unique_in_detector(),
         event_id_subset_of_detector_number(),
         NXdetector_pixel_offsets_are_unambiguous(),
     ]
diff --git a/tests/validators_test.py b/tests/validators_test.py
index 94b38ff..d5bb7e6 100644
--- a/tests/validators_test.py
+++ b/tests/validators_test.py
@@ -589,7 +589,9 @@ def test_NXlog_nested_top_dead_center_has_no_value():
     assert result.name == "chopper/top_dead_center"
 
 
-@pytest.mark.parametrize('value', [(1, 2, 3), np.array([1, 2, 3]), [[0, 1], [2, 3]]])
+@pytest.mark.parametrize(
+    'value', [[1, 2, 3], np.array([1, 2, 3]), np.array([[0, 1], [2, 3]])]
+)
 def test_duplicate_detector_number(value):
     det = chexus.Group(name="detector1", attrs={"NX_class": "NXdetector"})
     det.children = {
@@ -601,18 +603,12 @@ def test_duplicate_detector_number(value):
             parent=det,
         )
     }
-    det2 = chexus.Group(name="detector2", attrs={"NX_class": "NXdetector"})
-    det2.children = {
-        'detector_number': chexus.Dataset(
-            name="detector_number", value=[4, 5, 6], shape=(3,), dtype=int, parent=det2
-        )
-    }
-    assert chexus.validators.detector_numbers_unique_in_all_detectors().applies_to(det)
-    validator = chexus.validators.detector_numbers_unique_in_all_detectors()
+    assert chexus.validators.detector_numbers_unique_in_detector().applies_to(det)
+    validator = chexus.validators.detector_numbers_unique_in_detector()
     assert validator.validate(det) is None
-    assert validator.validate(det2) is None
-    # Second time the same detector numbers are seen, we expect a violation
-    assert validator.validate(det) is not None
+    # Make one entry duplicate
+    det.children['detector_number'].value[-1] = 1
+    assert isinstance(validator.validate(det), chexus.Violation)
 
 
 def test_event_id_not_in_detector_number():