diff --git a/session_3/session_3.Rmd b/session_3/session_3.Rmd
index 4156027493c0ce522ebb733d6c9aecdf864f57c6..d13d3d6d762b653baff64ffe67ba24fa913e7bcb 100644
--- a/session_3/session_3.Rmd
+++ b/session_3/session_3.Rmd
@@ -349,7 +349,7 @@ ggplot(data = diamonds, mapping = aes(x = cut, fill = cut)) +
 
 By combining the right **geom**, **coordinates** and **faceting** functions, you can build a large number of different plots to present your results.
 
-# See you in [R.4: data transformation](https://can.gitbiopages.ens-lyon.fr/R_basis/session_4/)
+# See you in [R.4: data transformation](https://can.gitbiopages.ens-lyon.fr/R_basis/session_4.html)
 
 # To go further:  animated plots from xls files