Create another symbol in specific point in a line graph

I would like to have another symbol in a specific point of line graphs where the x axis has value of 1. In my graph, all the points in the line have circle as a symbol, but I would like to have a triangle where the value of the x axis is 1.

So far, I found this post when it creates an X symbol, but when I use it on my code, it creates an X mark on top the circle while I want an entirely new symbol.

Here is the code:

library(ggplot2)

wd = "path/"

block.data = read.csv(paste0(wd, "block.data.csv"))

ggplot(data = block.data, aes(x = PSF, y = CC, group = 1)) +
  geom_line() +
  geom_point(size = 2) + 
  theme_bw() + 
  theme(panel.grid.major = element_blank(), panel.grid.minor = element_blank(),
        panel.background = element_blank(), axis.line = element_line(colour = "black")) + 
  scale_x_continuous(breaks = seq(0, 2, .2)) + 
  scale_y_continuous(breaks = seq(0.08, 23, .01))

And the dataset:
structure(list(PSF = c(0, 0.2, 0.4, 0.6, 0.8, 1, 1.2, 1.4, 1.6,
1.8, 2), CC = c(0.08278661, 0.1866827, 0.2051862, 0.218509, 0.2247673,
0.2268575, 0.2265966, 0.22522, 0.223409, 0.2213272, 0.2192285
)), class = "data.frame", row.names = c(NA, -11L))

One option would be to map a condition, i.e. PSF != 1 on the shape aes and set your desired shape using scale_shape_manual:

library(ggplot2)

ggplot(data = block.data, aes(x = PSF, y = CC, group = 1)) +
  geom_line() +
  geom_point(aes(shape = PSF != 1), size = 3) +
  scale_shape_manual(values = c(17, 16)) +
  theme_bw() +
  theme(
    panel.grid.major = element_blank(), panel.grid.minor = element_blank(),
    panel.background = element_blank(), axis.line = element_line(colour = "black")
  ) +
  scale_x_continuous(breaks = seq(0, 2, .2)) +
  scale_y_continuous(breaks = seq(0.08, 23, .01)) +
  guides(shape = "none")

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