Is this a MATLAB bode phase plot error?
You can add or subtract 360 deg (2*pi rad) as many times as needed in Bode phase graph. Right click in your graph, Properties &gt; Options &gt; Phase Response &gt; Adjust phase offsets [on] &gt; Keep phase close to [-pi] (in your case), At frequency [0.000]. Done in MATLAB R2015a.
Edit: still works in MATLAB R2020b.