# Mark clockwise angle with an arrow using tkz-euclide

How can I mark an angle going clockwise with an arrow in tkz-euclide? For now I have this

As you can see the arrow in red should point in the other direction but I haven't found a way to do it. Here is the code

\documentclass[a4paper,12pt]{book}

\usepackage{fontspec}
%math
\usepackage{amsmath,empheq}
\usepackage{mathtools}
\usepackage{amscd}
\usepackage{amsxtra}
\usepackage{amsthm}
\usepackage{unicode-math}
%tikz
\usepackage{tkz-euclide}
\usetkzobj{all}

\begin{document}

\begin{figure}[htbp]
\centering
\begin{tikzpicture}[scale=1]
\tkzInit[xmin=-4,ymin=-4,xmax=4,,ymax=4]
%\tkzClip
\tkzDefPoint(0,0){O}
\tkzDefPoint(4,0){A}
\tkzDefPoint(30:4){P}
\tkzDefPoint(-30:4){P'}
\tkzInterLL(P,P')(O,A) \tkzGetPoint{B}
\tkzDrawX[label=$x$,noticks,right space=0.3,left space=0.3,right=3pt]
\tkzDrawY[label=$y$,noticks,up space=0.3,down space=0.3,above=3pt]
\tkzDrawCircle(O,A)
\tkzDrawSegment[color=blue](P,B)
\tkzDrawSegment[color=red](B,P')
\tkzDrawSegments(O,P O,P')
\tkzMarkAngle[size=1,color=blue,arrows=-stealth](B,O,P)
\tkzLabelAngle[pos=1.5,color=blue](B,O,P) {$\alpha$}
\tkzMarkAngle[size=1,color=red,arrows=-stealth](P',O,B)
\tkzLabelAngle[pos=1.5,color=red](P',O,B) {$-\alpha$}
\tkzLabelPoints[below right](P')
\tkzLabelPoints[above right](P)
\tkzLabelPoints[below left](O)
\end{tikzpicture}
\caption{}
%\label{}
\end{figure}

\end{document}


\tkzMarkAngle[size=1,color=blue,arrows=stealth-](B,O,P)