© Twitter / JanetJackson
The singer's boyfriend Wissam Al Mana "gave her a huge, expensive ring" earlier this year, a source told Us Weekly.
"She's afraid it will get lost, so she keeps it locked up!" the friend added.
The pair, who have been dating since 2010, are planning to marry in the spring in Qatar. Al Mana, 37, is a luxury-brand mogul.
An insider predicted that the ceremony will "cost millions" as he is "flying in all of Janet's friends and family on private jets".
The source explained: "He wants to get a top chef to create a custom menu."
© Joseph Kerlakian/Rex Features
The couple reportedly want children and plan to adopt if they are unable to have their own.
