spectral arrows cause end warp beacon to go off

i was continuing my experiments with spectral arrows and i shot one into the warp portal in hopes that it would warp it. what i didnt expect to see was a beacon effect coming out the top. this beacon ray was yellow tinted and only lasted a few seconds but i later found out that it only worked about %75 of the time.

~~~_{HOW TO REPLICATE}~~~
1. go into end
2. find the warp portal (assuming you've already killed the dragon)
3. shoot a spectral arrow into it (most successful through the top or bottom)