get_gameObject is not allowed to be called during serialization

I get this error during build creation:
get_gameObject is not allowed to be called during serialization, call it from Awake or Start instead.
It's because of the following OnValidate() event handler:

void OnValidate()
{
#if UNITY_EDITOR

if (PrefabUtility.GetPrefabType(gameObject) != PrefabType.Prefab)​

#endif

{

DoSomething();​

}​

}

This is important editor functionality, but is not needed during building.
Is there an easy way to detect that we are running in build mode?

 

What are the exact field/property declarations you have in that script?