diff --git a/powertrain_build/interface/zone_controller.py b/powertrain_build/interface/zone_controller.py
index 3646e7e..078d4d1 100644
--- a/powertrain_build/interface/zone_controller.py
+++ b/powertrain_build/interface/zone_controller.py
@@ -142,7 +142,7 @@ class ZCAL(BaseApplication):
 
         raw = self.read_translation_files(definition)
         self.composition_spec = {
-            key: raw[key] for key in ("port_interfaces", "data_types", "calls", "Diagnostics") if key in raw
+            key: raw[key] for key in ("port_interfaces", "data_types", "calls", "diagnostics") if key in raw
         }
         ports_info = {}
         for port_name, port in raw.get("ports", {}).items():