diff --git a/src/pynxxas/models/nexus.py b/src/pynxxas/models/nexus.py
index 049f227..4ac29ab 100644
--- a/src/pynxxas/models/nexus.py
+++ b/src/pynxxas/models/nexus.py
@@ -103,7 +103,7 @@ class NxXasModel(NxClass, NxGroup, nx_class="NxXas"):
     mode: NxXasMode
     element: NxElement
     edge: NxEdge
-    calculated: bool = False
+    calculated: Optional[bool] = None
     energy: units.PydanticQuantity = units.as_quantity([])
     intensity: units.PydanticQuantity = units.as_quantity([])
     title: Optional[str] = None
diff --git a/src/pynxxas/tests/test_nexus.py b/src/pynxxas/tests/test_nexus.py
index 3af4cca..c504510 100644
--- a/src/pynxxas/tests/test_nexus.py
+++ b/src/pynxxas/tests/test_nexus.py
@@ -83,7 +83,7 @@ def _expected_content(nx_class, energy, intensity):
         "intensity": intensity,
         "title": "Fe K (transmission)",
         "instrument": None,
-        "calculated": False,
+        "calculated": None,
         "plot": {
             "NX_class": "NXdata",
             "axes": [