Benchmark for sharpe ratio

[noowfel]

vbt is a beautiful tool, thank you for the work!
I am having issues with the benchmark for sharpe ratio calculations.

following what was said here : #247 (reply in thread)
I tried to set a benchmark for the sharpe_ratio but it seems to be ignored. Using :

pf.sharpe_ratio(benchmark_rets=...)
regardless of what I pass as benchmark_rets, the sharpe_ratio resulting does not change.

Instead I was able to set the risk free rate directly with :
pf.sharpe_ratio(risk_free=0)

What am I missing ?
Thanks