diff --git a/man/setkey.Rd b/man/setkey.Rd
index 96e293fd2..f15373c94 100644
--- a/man/setkey.Rd
+++ b/man/setkey.Rd
@@ -110,7 +110,7 @@ reference.
 \references{
   \url{https://en.wikipedia.org/wiki/Radix_sort}\cr
   \url{https://en.wikipedia.org/wiki/Counting_sort}\cr
-  \url{http://stereopsis.com/radix.html}\cr
+  \url{https://stereopsis.com/radix.html}\cr
   \url{https://codercorner.com/RadixSortRevisited.htm}\cr
   \url{https://cran.r-project.org/package=bit64}\cr
   \url{https://github.com/Rdatatable/data.table/wiki/Presentations}
diff --git a/man/setorder.Rd b/man/setorder.Rd
index c810048d4..b4a346cf1 100644
--- a/man/setorder.Rd
+++ b/man/setorder.Rd
@@ -113,7 +113,7 @@ If you require a copy, take a copy first (using \code{DT2 = copy(DT)}). See
 \references{
   \url{https://en.wikipedia.org/wiki/Radix_sort}\cr
   \url{https://en.wikipedia.org/wiki/Counting_sort}\cr
-  \url{http://stereopsis.com/radix.html}\cr
+  \url{https://stereopsis.com/radix.html}\cr
   \url{https://codercorner.com/RadixSortRevisited.htm}\cr
   \url{https://medium.com/basecs/getting-to-the-root-of-sorting-with-radix-sort-f8e9240d4224}
 }