Underground jungle changes into the cavern layer

[BumbleClumps]

Hello Everyone,
I have made an arena for killing expert Plantera, a fairly big arena. When I attempted the fight, I noticed that the Plantera was enraged, and was oblivious to why. It turned out that the music changed in the middle of the area, which implys a new biome. Is their a way to change this other biome back to jungle?
Thank you
B

 

[r4v1n6]

To get the jungle biome you need 80+ jungle blocks (mud with jungle grass, Lihzard temple blocks) within a distance of 50 tiles around the player. It sounds like your arena is larger than that.

You could place some jungle blocks in the middle of the arena. If they are in the way, you could actuate them.

 

[BumbleClumps]

To get the jungle biome you need 80+ jungle blocks (mud with jungle grass, Lihzard temple blocks) within a distance of 50 tiles around the player. It sounds like your arena is larger than that.

You could place some jungle blocks in the middle of the arena. If they are in the way, you could actuate them.

Will try that, thank you!
Edit: It worked!