[R-SIG-Finance] segments could not draw line in log plot

[Wind]

The following code show the vertical red line successfully.
y<-1:100
plot(y)
segments(50,0,50,100,col='red')

But, if the y axis is changed to log axis, the red line could not be drawn.
y<-1:100
plot(y,log='y')
segments(50,0,50,100,col='red')

I wonder whether there is some method to draw a vertical line in a log-axis plot?
Thanks in advance.