diff --git a/smoketest/scenarios/50-stale-system.sh b/smoketest/scenarios/50-stale-system.sh
index c5d1f34..0e576c7 100644
--- a/smoketest/scenarios/50-stale-system.sh
+++ b/smoketest/scenarios/50-stale-system.sh
@@ -9,11 +9,22 @@ scenario() {
   date="$(date -d '30 days ago' +%Y/%m/%d)"
 
   # Go back to Arch as it was a month ago, from the Arch Linux Archive, which
-  # is also a mirror that stopped syncing a month ago
+  # is also a mirror that stopped syncing a month ago. Packages from Arch's
+  # repos that the archive doesn't have yet, often split off since (e.g.
+  # clang-libs from clang), go first: their files conflict with the old
+  # packages'. update installs them again
   run_in_vm downgrade "set -e
+    pacman -Qqn | sort > ~/native-now
     echo 'Server = https://archive.archlinux.org/repos/$date/\$repo/os/\$arch' \
       | sudo tee /etc/pacman.d/mirrorlist
-    sudo pacman -Syyuu --noconfirm"
+    sudo pacman -Syy
+    newer=\"\$(pacman -Qqm | sort | comm -12 ~/native-now -)\"
+    rm ~/native-now
+    if [ -n \"\$newer\" ]; then
+      echo \"Not in the archive yet, removing: \"\$newer
+      sudo pacman -Rdd --noconfirm \$newer
+    fi
+    sudo pacman -Suu --noconfirm"
   [ "$STATUS" -eq 0 ] || skip "couldn't downgrade to Arch as of $date (see $LAST_LOG)"
   vm_reboot
   kernel_before="$(vm_value 'uname -r')"