ezdxf breaks dynamic blocks

[gswifort]

I have a drawing with a dynamic block. I load it and save it using ezdxf (I don't do anything else). After saving the block is still dynamic, but if I copy it (Ctrl+C → Ctrl+V), the copied block is no longer dynamic.

I know that ezdxf doesn't support dynamic blocks, but as the documentation says:

ezdxf also has no support or these features beyond the preservation of these undocumented DXF entities.

import ezdxf

doc = ezdxf.readfile("test.dxf")
doc.saveas("test2.dxf")

test.zip