diff --git a/powertrain_build/zone_controller/composition_yaml.py b/powertrain_build/zone_controller/composition_yaml.py
index 446ef7a..2cc8bb4 100644
--- a/powertrain_build/zone_controller/composition_yaml.py
+++ b/powertrain_build/zone_controller/composition_yaml.py
@@ -305,7 +305,7 @@ class CompositionYaml(ProblemLogger):
             (dict): Dict containing diagnostic information.
         """
         diag_dict = {}
-        diagnostics = self.composition_spec.get("Diagnostics", {})
+        diagnostics = self.composition_spec.get("diagnostics", {})
         dids = diagnostics.get("dids", {})
         self.zc_dids.valid_dids = dids
         events = diagnostics.get("events", {})
diff --git a/tests/zone_controller/test_composition_yaml.py b/tests/zone_controller/test_composition_yaml.py
index 8e140e4..9eedd20 100644
--- a/tests/zone_controller/test_composition_yaml.py
+++ b/tests/zone_controller/test_composition_yaml.py
@@ -172,7 +172,7 @@ class TestCompositionYaml(unittest.TestCase):
     def test_composition_yaml_with_dids(self):
         """Checking that the dict is generated correctly, with DIDs."""
         self.zc_dids.project_dids = {"DID1": {"type": "UInt8"}}
-        self.zc_spec["Diagnostics"] = composition_yaml_with_dids.diagnostics
+        self.zc_spec["diagnostics"] = composition_yaml_with_dids.diagnostics
         with patch.object(
             CompositionYaml,
             "_get_all_calibration_definitions",
@@ -187,7 +187,7 @@ class TestCompositionYaml(unittest.TestCase):
     def test_composition_yaml_with_dtcs(self):
         """Checking that the dict is generated correctly, with DTCs."""
         self.zc_core.project_dtcs = {"DTC1"}
-        self.zc_spec["Diagnostics"] = composition_yaml_with_dtcs.diagnostics
+        self.zc_spec["diagnostics"] = composition_yaml_with_dtcs.diagnostics
         with patch.object(
             CompositionYaml,
             "_get_all_calibration_definitions",