OnPostprocessAllAssets is not doing anything

I have implemented this based on the information here, except converted it to C# http://unity3d.com/support/documentation/ScriptReference/AssetPostprocessor.OnPostprocessAllAssets.html However, it never seems to get called, no matter what I import, move, or delete. Am I doing something wrong or is this thing broken? Other AssetPostprocessor methods seem to work.

public class AssetsImport : AssetPostprocessor
{
	void OnPostprocessAllAssets(string[] importedAssets, string[] deletedAssets, string[] movedAssets, string[] movedFromAssetPaths)
	{
		Debug.Log("Imported Assets:");
		foreach (string asset in importedAssets)
		{
			Debug.Log(asset);
		}
		Debug.Log("Deleted Assets:");
		foreach (string asset in deletedAssets)
		{
			Debug.Log(asset);
		}
		Debug.Log("Moved Assets:");
		for (int i = 0; i < movedAssets.Length; i++)
		{
			Debug.Log("From " + movedFromAssetPaths[i] + " to " + movedAssets[i]);
		}
	}
}