How to make scatterplot with colors based on a column and add a mean line through stats_summary with grouping based on another column?

I have a data.frame (see below) and I would like to build a scatterplot, where colours of dots is based on a factor column (replicate). I simultaneously want to add a line that represents the mean of y, for each x. The problem is that when I define the stat_summary it uses the colours I requested for groupingand hence I get three mean lines (for each color) instead of one. Trying to redefine groups either in ggplot() or stat_summary() function did not work.

if I disable colors I get what I want (a single mean line).

How do I have colors (plot # 1), yet still have a single mean line (plot # 2)?

structure(list(conc = c(10L, 10L, 10L, 25L, 25L, 25L, 50L, 50L, 
    50L, 75L, 75L, 75L, 100L, 100L, 100L, 200L, 200L, 200L, 300L, 
    300L, 300L, 400L, 400L, 400L, 500L, 500L, 500L, 750L, 750L, 750L, 
    1000L, 1000L, 1000L), citric_acid = c(484009.63, 409245.09, 303193.26, 
    426427.47, 332657.35, 330875.96, 447093.71, 344837.39, 302873.98, 
    435321.69, 359146.09, 341760.28, 378298.37, 342970.87, 323146.92, 
    362396.98, 361246.41, 290638.14, 417357.82, 351927.66, 323611.37, 
    416280.3, 359430.65, 327950.99, 431167.14, 361429.91, 291901.43, 
    340166.41, 353640.91, 341839.08, 393392.69, 311375.19, 342103.54
    ), MICIT = c(20771.28, 18041.97, 12924.35, 49814.13, 38683.32, 
    38384.72, 106812.16, 82143.12, 72342.43, 156535.39, 128672.12, 
    119397.14, 187208.46, 167814.92, 159418.62, 350813.47, 357227.48, 
    295948.31, 505553.77, 523282.46, 489652.3, 803544.84, 704431.61, 
    654753.29, 1030485.41, 895451.64, 717698.52, 1246839.19, 1309712.63, 
    1212111.53, 1930503.38, 1499838.89, 1642091.64), replicate = structure(c(1L, 
    2L, 3L, 1L, 2L, 3L, 1L, 2L, 3L, 1L, 2L, 3L, 1L, 2L, 3L, 1L, 2L, 
    3L, 1L, 2L, 3L, 1L, 2L, 3L, 1L, 2L, 3L, 1L, 2L, 3L, 1L, 2L, 3L
    ), .Label = c("1", "2", "3"), class = "factor"), MICITNorm = c(0.0429150139016862, 
    0.0440859779160698, 0.0426274317575529, 0.116817357005636, 0.116285781751102, 
    0.116009395182412, 0.238903293897827, 0.238208275500519, 0.238853235263062, 
    0.359585551549246, 0.358272367659634, 0.34935932285636, 0.494869856298879, 
    0.489297881187402, 0.493331701877276, 0.968036405822146, 0.98887482369721, 
    1.01827072661558, 1.21131974956166, 1.48690347328766, 1.51308744189056, 
    1.93029754230503, 1.95985403582026, 1.99649737297637, 2.38999059622215, 
    2.47752500616233, 2.45870162403795, 3.6653801002868, 3.70350995307641, 
    3.54585417793659, 4.90731889298706, 4.81682207885606, 4.79998435561351
    )), class = "data.frame", row.names = c(NA, -33L))

ggplot(xx, aes (conc, MICIT, colour = replicate)) + geom_point () +
            stat_summary(geom = "line", fun = mean)

>Solution :

Use aes(group = 1):

ggplot(xx, aes(conc, MICIT, colour = replicate)) + 
  geom_point() +
  geom_line() +
  stat_summary(aes(group = 1), geom = "line", fun = mean)