MythicMobs Start error

this error appear when i started the server Please someone help me

System:

• Version: Paper 1.16.5
• Java: 11

[13:29:22 ERROR]: Error occurred while enabling MythicMobs v4.12.0-FREE (Is it up to date?)

java.lang.VerifyError: Bad return type

Exception Details:

Location:

javassist/f.b(Ljava/lang/String;Z)Ljavassist/CtClass; @67: areturn

Reason:

Type 'javassist/l' (current frame, stack[0]) is not assignable to 'javassist/CtClass' (from method signature)

Current Frame:

bci: @67

flags: { }

locals: { 'javassist/f', 'java/lang/String' }

stack: { 'javassist/l' }

Bytecode:

0000000: 2b03 b600 9510 5ba0 0008 2bb8 00a1 4c2b

0000010: 12a3 b600 a799 002f 2b03 2b10 5bb6 00ab

0000020: b600 af4e 1c99 000b 2a2d b600 87c7 000d

0000030: 2a2d b600 b2c7 0005 01b0 bb00 b459 2b2a

0000040: b700 b7b0 2a2b b600 b2c7 0005 01b0 bb00

0000050: 8059 2b2a b700 b8b0

Stackmap Table:

same_frame(@15)

full_frame(@48,{Object[#2 (closed)],Object[#126 (closed)],Top,Object[#126 (closed)]},{})

chop_frame(@58,2)

same_frame(@68)

same_frame(@78)