How do I undo a stroke of grease pencil?

How do I undo a stroke of grease pencil? It seems that it can only be erased.

Ctrl+z should do it just fine

@Sago: Really? I tried but it only undo the mesh operations, not grease pencil strokes.

what version do you have? I tried on an old version (2.58) and 2.62 (before bmesh merge). Works in both.