pROC ROC curves remove empty space

Question

I want to draw ROC curves with pRoC. However for some reason there is extra empty space on either side of the x-axis and I cannot remove it with xlim. Some example code:

Answer 1

There is yet a third answer, which takes the margins out of the plotting region, so it will automatically look squared, even when the device isnt. This is done by setting the graphical parameter pty to "s":

library(pROC)
par(pty = "s")
n = c(4, 3, 5) 
b = c(TRUE, FALSE, TRUE)
rocobj <- plot.roc(b, n, percent = TRUE, main="ROC", col="#1c61b6", add=FALSE, asp = NA)

(I added a black frame to visualize what's going on)