Country singer Blake Shelton and Gwen Stefani are reportedly planning to get married during Christmas this year, after dating for nearly eight months. However, a prenuptial agreement is apparently become a thorn in their relationship that has blossomed since the two came together on the sets of The Voice.

According to OK! Magazine, the Hollaback Girl hit-maker is planning to have a heated talk with the country singer over their prenuptial agreement.

"She's already floated the idea of a prenup," a source told the gossip site (via Inquisitr). "Gwen's worth almost twice as much as Blake, and from her experience with Gavin, she knows she has to prepare for the worst."

The lead singer of No Doubt has a $100m (£76m) fortune and split from former husband Gavin Rossdale after 10 years of marriage. The duo have three children together – Zuma, 7, Kingston, 10, and two-year-old Apollo.

"What happened before has hardened her," the source said. "[Stefani does] not want to make the same mistakes."

While Shelton and Stefani's road to marriage may be laid with some tough negotiations, the couple seem to be almost certain of taking their relationship to the next level.

"Everyone can see how happy they are," the source said. "Gwen has told friends she doesn't suit being single and is ready to start the next chapter."

However, Shelton has reportedly not yet proposed marriage to Stefani, even though the 46-year-old songstress has been spotted wearing an engagement ring on numerous occasions.

"They are not engaged yet," a source told People Magazine. "Everyone is expecting it to happen at some point, though." An insider close to the couple added: "There are no immediate plans for their future, but it's a serious relationship."