Object prototypes are not copied in version 2.1 , works in 0.63

[gpitot]

Example of working copy of object prototype here in version 0.63
https://codesandbox.io/s/deepcopy-0-6-3-prototype-0hir2?file=/src/index.js

Example of non-working copy of object prototype here in version 2.1
https://codesandbox.io/s/deepcopy-2-1-prototype-54r45?file=/src/index.js