diff --git a/fluent-package/apt/systemd-test/update-from-v4.sh b/fluent-package/apt/systemd-test/update-from-v4.sh
index c2c0f8f2..67593c4e 100755
--- a/fluent-package/apt/systemd-test/update-from-v4.sh
+++ b/fluent-package/apt/systemd-test/update-from-v4.sh
@@ -9,6 +9,7 @@ sudo apt install -y curl ca-certificates
 curl -fsSL https://toolbelt.treasuredata.com/sh/install-${distribution}-${code_name}-td-agent4.sh | sh
 
 systemctl status --no-pager td-agent
+main_pid=$(eval $(systemctl show td-agent --property=MainPID) && echo $MainPID)
 
 # Generate garbage files
 touch /etc/td-agent/a\ b\ c
@@ -49,6 +50,9 @@ esac
 systemctl status --no-pager fluentd
 systemctl status --no-pager td-agent
 
+# Fluentd should be restarted when update from v4.
+test $main_pid -ne $(eval $(systemctl show fluentd --property=MainPID) && echo $MainPID)
+
 # Test: restoring td-agent service alias
 sudo systemctl stop fluentd
 sudo systemctl unmask td-agent
diff --git a/fluent-package/yum/systemd-test/update-from-v4.sh b/fluent-package/yum/systemd-test/update-from-v4.sh
index 39626673..e7697602 100755
--- a/fluent-package/yum/systemd-test/update-from-v4.sh
+++ b/fluent-package/yum/systemd-test/update-from-v4.sh
@@ -19,6 +19,7 @@ sudo $DNF install -y td-agent-${td_agent_version}-1.*.x86_64
 
 sudo systemctl enable --now td-agent
 systemctl status --no-pager td-agent
+main_pid=$(eval $(systemctl show td-agent --property=MainPID) && echo $MainPID)
 
 # Generate garbage files
 touch /etc/td-agent/a\ b\ c
@@ -40,6 +41,9 @@ systemctl status --no-pager fluentd # Migration process starts the service autom
 sudo systemctl enable fluentd # Enable the unit name alias
 systemctl status --no-pager td-agent
 
+# Fluentd should be restarted when update from v4.
+test $main_pid -ne $(eval $(systemctl show fluentd --property=MainPID) && echo $MainPID)
+
 # Test: config migration
 test -h /etc/td-agent
 test -h /etc/fluent/fluentd.conf