diff --git a/ctapipe/core/tests/test_traits.py b/ctapipe/core/tests/test_traits.py
index abf2aaebf71..64d27a6733f 100644
--- a/ctapipe/core/tests/test_traits.py
+++ b/ctapipe/core/tests/test_traits.py
@@ -298,6 +298,13 @@ def test_telescope_parameter_lookup_by_type(mock_subarray):
     assert lookup["LST_LST_LSTCam"] == 100
     assert lookup["MST_MST_MSTCam"] == 10
 
+    # no global default
+    lookup = TelescopeParameterLookup([("type", "LST*", 100)])
+    lookup.attach_subarray(mock_subarray)
+    assert lookup["LST_LST_LSTCam"] == 100
+    with pytest.raises(KeyError):
+        assert lookup["MST_MST_MSTCam"] == 10
+
 
 def test_telescope_parameter_patterns(mock_subarray):
     """Test validation of TelescopeParameters"""
diff --git a/ctapipe/core/traits.py b/ctapipe/core/traits.py
index d9a51739b78..9a9975dfba4 100644
--- a/ctapipe/core/traits.py
+++ b/ctapipe/core/traits.py
@@ -393,12 +393,10 @@ def __init__(self, telescope_parameter_list):
         self._value_for_tel_id = None
         self._value_for_type = None
         self._subarray = None
-        self._subarray_global_value = None
-        self._subarray_global_value_set = False
+        self._subarray_global_value = Undefined
         for param in telescope_parameter_list:
             if param[1] == "*":
                 self._subarray_global_value = param[2]
-                self._subarray_global_value_set = True
 
     def attach_subarray(self, subarray):
         """
@@ -440,7 +438,7 @@ def __getitem__(self, tel: Optional[Union[int, str]]):
         Returns the resolved parameter for the given telescope id
         """
         if tel is None:
-            if self._subarray_global_value_set:
+            if self._subarray_global_value is not Undefined:
                 return self._subarray_global_value
 
             raise KeyError("No subarray global value set for TelescopeParameter")
@@ -464,7 +462,7 @@ def __getitem__(self, tel: Optional[Union[int, str]]):
 
         if isinstance(tel, str):
             try:
-                if self._subarray_global_value_set:
+                if self._subarray_global_value is not Undefined:
                     return self._value_for_type.get(tel, self._subarray_global_value)
                 return self._value_for_type[tel]
             except KeyError: