undefined reference to gSwarmTableLength error when building CFRU

[topyke]

when I try to build my CFRU hack into a test rom, it throws the following error:

C://devkitPro//devkitARM//bin/arm-none-eabi-ld: warning: build/linked.o has a LOAD segment with RWX permissions
C://devkitPro//devkitARM//bin/arm-none-eabi-ld: ./build\93544cbfeaccb40e58088fd3882f85bf.o: in function `TryGenerateWildMon': wild_encounter.c:(.text+0x8cc): undefined reference to `gSwarmTableLength'
C://devkitPro//devkitARM//bin/arm-none-eabi-ld: ./build\93544cbfeaccb40e58088fd3882f85bf.o: in function `TryUpdateSwarm':
wild_encounter.c:(.text+0xb34): undefined reference to `gSwarmTableLength'

I don't know what to do to fix this issue, can anyone help me?