apps/fft FFT does not run with size of 256 x 256

[impao]

Hi,

I download and build apps/fft OK and run OK with
./bench_fft 128 128

But with
./bench_fft 256 256

it aborts with
+++
Internal error at /xx/Halide-master/src/IR.cpp:250 triggered by user code at ./main.cpp:107:
Condition failed: lanes > 1
Ramp of lanes <= 1
Abort trap: 6
+++

Any suggestions would be appreciated!