Kendall Jenner is "scared" about her sister Kylie turning 18.

Kendall and Kylie Jenner

Kendall and Kylie Jenner

The 'Keeping Up With The Kardashians' star reaches the milestone on Monday (10.08.15) and her 19-year-old sibling appears to be worried about what antics she'll get up to.

She wrote on Instagram: "Weekend vibes #KyliesTurning18ImScared. (sic)"

Meanwhile, it was previously revealed that Kylie will be paid over $100,000 to celebrate her own birthday at the Beachclub Montreal in Canada.

The club owner Olivier Primeau is said to have also organised for the 17-year-old beauty to be wined and dined on a luxury boat just off the island, before being treated to a $3,000 birthday cake.

And Kylie previously admitted she was looking forward to going out for the first time "legally" without a chaperone.

She said: "What the first thing I want to do is maybe have like a birthday party and then maybe go on a trip with just my friends. I'm legal, so I can go on a trip legally without a chaperone, so that'll be fun, just a girl trip."

Of her birthday plans, she added: "I'm going to be 18! So [it will be] crazy!"