diff --git a/workers/unity/Packages/io.improbable.worker.sdk/CEventTrace.cs b/workers/unity/Packages/io.improbable.worker.sdk/CEventTrace.cs
index 969cd87413..a2f306947c 100644
--- a/workers/unity/Packages/io.improbable.worker.sdk/CEventTrace.cs
+++ b/workers/unity/Packages/io.improbable.worker.sdk/CEventTrace.cs
@@ -60,7 +60,7 @@ public struct SpanId
             public fixed Char Data[16];
         }
 
-        public enum ItemType
+        public enum ItemType : byte
         {
             Span = 1,
             Event = 2