Drawing using ofGetMousePressed() inside draw() causes flickering

I was trying one of the firsts examples inside the Graphics section of ofBook and noticed something odd. When creating a simple brush using 2D primitives, once I release the mouse the last shape that has been drawn flickers.

Here is the code:

void ofApp::setup(){
    ofSetBackgroundAuto(false);
}

void ofApp::draw(){

    if (ofGetMousePressed(OF_MOUSE_BUTTON_LEFT)) {
        ofSetColor(ofRandom(255), ofRandom(255), ofRandom(255));
        ofDrawCircle(ofGetMouseX(), ofGetMouseY(), 20);
    }
}

I've tried to upload a video to show what's happening but the online compression makes the flickering go away.

OpenFrameworks 0.9.3
XCode 7.3.1
OSX 10.11.6
Macbook Pro 11,5

Use the ofBook Brushes with Basic Shapes example and the supplied setup() and draw() code as the reproduction. Compare behavior while the mouse is pressed and after release; done means the final circle no longer flickers after release, with the behavior checked on the stated OpenFrameworks 0.9.3, Xcode 7.3.1, and macOS setup.