Problem with X11

Dear All,
I have never had this problem before. I run debian testing on my box
and I have recently update my R environment.
Now, see what happens when I try the most trivial of all plots

plot(seq(22))

Error in (function (display = "", width, height, pointsize, gamma, bg,
:
  X11 module cannot be loaded
  In addition: Warning message:
  In (function (display = "", width, height, pointsize, gamma, bg,  :
    unable to load shared object '/usr/lib/R/modules//R_X11.so':
      /usr/lib/x86_64-linux-gnu/libpng12.so.0: version `PNG12_0' not
      found (required by /usr/lib/R/modules//R_X11.so)

and this is my sessionInfo()

sessionInfo()

R version 3.2.4 Revised (2016-03-16 r70336)
Platform: x86_64-pc-linux-gnu (64-bit)
Running under: Debian GNU/Linux stretch/sid

locale:
 [1] LC_CTYPE=en_GB.utf8       LC_NUMERIC=C
  [3] LC_TIME=en_GB.utf8        LC_COLLATE=en_GB.utf8
   [5] LC_MONETARY=en_GB.utf8    LC_MESSAGES=en_GB.utf8
    [7] LC_PAPER=en_GB.utf8       LC_NAME=C
     [9] LC_ADDRESS=C              LC_TELEPHONE=C
     [11] LC_MEASUREMENT=en_GB.utf8 LC_IDENTIFICATION=C

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base


Anybody understands what is going on here?
Regards

Lorenzo