diff --git a/ci/scripts/msys2_system_upgrade_phase1.sh b/ci/scripts/msys2_system_upgrade_phase1.sh
index 0839228f419..aecd3089332 100755
--- a/ci/scripts/msys2_system_upgrade_phase1.sh
+++ b/ci/scripts/msys2_system_upgrade_phase1.sh
@@ -20,6 +20,9 @@
 set -eux
 
 # https://www.msys2.org/news/#2020-06-29-new-packagers
+msys2_repo_base_url=https://repo.msys2.org/msys
+# Mirror
+msys2_repo_base_url=https://sourceforge.net/projects/msys2/files/REPOS/MSYS2
 msys2_keyring_pkg=msys2-keyring-r21.b39fb11-1-any.pkg.tar.xz
 for suffix in "" ".sig"; do
   curl \
@@ -27,7 +30,7 @@ for suffix in "" ".sig"; do
     --remote-name \
     --show-error \
     --silent \
-    https://repo.msys2.org/msys/x86_64/${msys2_keyring_pkg}${suffix}
+    ${msys2_repo_base_url}/x86_64/${msys2_keyring_pkg}${suffix}
 done
 pacman-key --verify ${msys2_keyring_pkg}.sig
 pacman \
diff --git a/ci/scripts/r_windows_build.sh b/ci/scripts/r_windows_build.sh
index b084975fb12..cb33e676a7d 100755
--- a/ci/scripts/r_windows_build.sh
+++ b/ci/scripts/r_windows_build.sh
@@ -27,8 +27,14 @@ if [ "$RTOOLS_VERSION" = "35" ]; then
   # Use rtools-backports if building with rtools35
   curl https://raw.githubusercontent.com/r-windows/rtools-backports/master/pacman.conf > /etc/pacman.conf
   # Update keys: https://www.msys2.org/news/#2020-06-29-new-packagers
-  curl -OSsl "http://repo.msys2.org/msys/x86_64/msys2-keyring-r21.b39fb11-1-any.pkg.tar.xz"
+  msys2_repo_base_url=https://repo.msys2.org/msys
+  # Mirror
+  msys2_repo_base_url=https://sourceforge.net/projects/msys2/files/REPOS/MSYS2
+  curl -OSsL "${msys2_repo_base_url}/x86_64/msys2-keyring-r21.b39fb11-1-any.pkg.tar.xz"
   pacman -U --noconfirm msys2-keyring-r21.b39fb11-1-any.pkg.tar.xz && rm msys2-keyring-r21.b39fb11-1-any.pkg.tar.xz
+  # Use sf.net instead of http://repo.msys2.org/ temporary.
+  sed -i -e "s,^Server = http://repo\.msys2\.org/msys,Server = ${msys2_repo_base_url},g" \
+    /etc/pacman.conf
   pacman --noconfirm -Scc
   pacman --noconfirm -Syy
   # lib-4.9.3 is for libraries compiled with gcc 4.9 (Rtools 3.5)