plotting – Imaginary variables in ImplicitRegion

I am using the function ImplicitRegion[].

RegionPlot[ImplicitRegion[x^2 + y^2 == -1, {x, y}]]

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which gives me a circle, though in the documentation variables are said to be real.

Adding additional assumption does not change anything:

RegionPlot[ Assuming[{x, y} [Element] Reals, 
  ImplicitRegion[   x^2 + y^2 == -1, {{x, -[Pi], [Pi]}, {y, -[Pi], [Pi]}}]]]

How to fix this issue?