diff --git a/options/auto-upgrade.nix b/options/auto-upgrade.nix
index cc6a459..4861c40 100644
--- a/options/auto-upgrade.nix
+++ b/options/auto-upgrade.nix
@@ -19,7 +19,7 @@ in
 
     config = mkIf cfg.enable {
         systemd.services.nixos-upgrade.script = mkOverride 50 (
-            let 
+            let
                 nixos-rebuild = "${config.system.build.nixos-rebuild}/bin/nixos-rebuild";
                 date = "${pkgs.coreutils}/bin/date";
                 readlink = "${pkgs.coreutils}/bin/readlink";
@@ -29,26 +29,23 @@ in
                 upgradeFlag = optional (cfg.channel == null) "--upgrade";
             in ''
                 set -o pipefail
-                
-                upgrade() {
-                    ${nixos-rebuild} ${cfg.operation} ${toString (cfg.flags ++ upgradeFlag)}
-                }
-                
+
                 indent()
                 {
                     while read -r line ; do
                         echo "  $line"
                     done <<< "$1"
                 }
-                
+
                 start_time="$(${date})"
                 reboot_allowed="no"
+                activate_configuration="yes"
                 do_reboot="no"
                 exit_code=0
-                
+
                 ${optionalString cfg.allowReboot ''
                 reboot_allowed="yes"
-                
+
                 ${optionalString (cfg.rebootWindow != null) ''
                 current_time="$(${date} +%H:%M)"
                 lower="${cfg.rebootWindow.lower}"
@@ -74,10 +71,8 @@ in
                 ''}
 
                 output_file="$(mktemp)"
-                upgrade 2>&1 | tee "$output_file" || exit_code=$?
-                upgrade_output="$(cat "$output_file")"
-                rm -f "$output_file"
-                
+                ${nixos-rebuild} boot ${toString (cfg.flags ++ upgradeFlag)} 2>&1 | tee "$output_file" || exit_code=$?
+
                 send_email=no
                 email_subject="Upgrade succeeded"
                 email_body="The system upgrade started at $start_time has succeeded."
@@ -86,30 +81,15 @@ in
                     email_subject="Upgrade failed (exit code $exit_code)"
                     email_body="The system upgrade started at $start_time has failed with exit code $exit_code."
                 fi
-                
-                possible_warnings="$(${grep} -e "^trace:" <<<"$upgrade_output" || true)"
-                if [ "$possible_warnings" != "" ] ; then
-                    send_email=yes
-                    email_subject="$email_subject with warnings"
-                    email_body="$(cat <<-EOF
-                $email_body
-        
-        
-                These trace messages and warnings were encountered:
-                ---------------------------------------------------
-                $possible_warnings
-                EOF
-                    )"
-                fi
-                
+
                 booted_version="$(${readlink} /run/booted-system/{initrd,kernel,kernel-modules})"
                 built_version="$(${readlink} /nix/var/nix/profiles/system/{initrd,kernel,kernel-modules})"
-                
+
                 if [ "$booted_version" != "$built_version" ] ; then
                     version_comparison="$(cat <<-EOF
                 The booted kernel version
                 $(indent "$booted_version")
-                does not match currently active
+                does not match the newly built
                 $(indent "$built_version")
                 .
                 EOF
@@ -119,19 +99,48 @@ in
                     email_subject="$email_subject, reboot required"
                     email_body="$(cat <<-EOF
                 $email_body
-        
-        
+
+
                 A reboot is required, because:
                 ------------------------------
                 $version_comparison
                 EOF
                     )"
+                    activate_configuration="no"
                     if [ "$reboot_allowed" = "yes" ] && [ $exit_code -eq 0 ] ; then
                         email_body="$(printf "%s\n%s" "$email_body" "The system will reboot now.")"
                         do_reboot="yes"
+                        activate_configuration="yes"
+                    else
+                        email_body="$(printf "%s\n%s" "$email_body" "The upgraded configuration will be activated on the next reboot.")"
                     fi
                 fi
-                
+
+                ${optionalString (cfg.operation == "switch") ''
+                if [ "$activate_configuration" = "yes" ] ; then
+                    echo "Activating new configuration."
+                    ${nixos-rebuild} switch ${toString cfg.flags} 2>&1 | tee -a "$output_file" || exit_code=$?
+                fi
+                ''}
+
+                upgrade_output="$(cat "$output_file")"
+                rm -f "$output_file"
+
+                possible_warnings="$(${grep} -e "^trace:" <<<"$upgrade_output" || true)"
+                if [ "$possible_warnings" != "" ] ; then
+                    send_email=yes
+                    email_subject="$email_subject with warnings"
+                    email_body="$(cat <<-EOF
+                $email_body
+
+
+                These trace messages and warnings were encountered:
+                ---------------------------------------------------
+                $possible_warnings
+                EOF
+                    )"
+                fi
+
                 ${optionalString cfg.sendEmail ''
                 if [ "$send_email" = "yes" ] ; then
                     ${sendmail} -t -X - <<-EOF
@@ -141,22 +150,22 @@ in
                 Content-Transfer-Encoding: 8bit
                 Content-Type: text/plain; charset=UTF-8
                 X-Priority: 3
-        
+
                 $email_body
-        
-        
+
+
                 Full upgrade output:
                 --------------------
                 $upgrade_output
                 EOF
                 fi
                 ''}
-                
+
                 if [ "$do_reboot" = "yes" ] ; then
                     echo "Rebooting system."
                     ${shutdown} -r +1
                 fi
-                
+
                 exit $exit_code
             ''
         );