diff --git a/lib/CalDAV/OrganizerValidationPlugin.php b/lib/CalDAV/OrganizerValidationPlugin.php
index d768a49b..8fa2b2b7 100644
--- a/lib/CalDAV/OrganizerValidationPlugin.php
+++ b/lib/CalDAV/OrganizerValidationPlugin.php
@@ -22,6 +22,7 @@ function initialize(Server $server) {
         $this->server = $server;
         $server->on('calendarObjectChange', [$this, 'calendarObjectChange'], Plugin::PRIORITY_BEFORE_SCHEDULING - 10);
         $server->on('beforeMove', [$this, 'beforeMove'], 45);
+        $server->on('beforeCopy', [$this, 'beforeCopy'], 45);
     }
 
     function getPluginName() {
@@ -55,8 +56,15 @@ function calendarObjectChange(
     }
 
     function beforeMove($sourcePath, $destinationPath) {
+        // A team calendar lives in its own calendar home, so a legitimate MOVE into one always
+        // crosses homes. Exempt exactly that destination from the guard, because it is the one
+        // the ORGANIZER validation below covers instead.
         list($calendarPath,) = Utils::splitEventPath('/' . ltrim($destinationPath, '/'));
-        if (!$calendarPath || !$this->isTeamCalendarPath($calendarPath)) return;
+        if (!$calendarPath || !$this->isTeamCalendarPath($calendarPath)) {
+            $this->assertSameCalendarHome($sourcePath, $destinationPath);
+
+            return;
+        }
 
         try {
             $source = $this->server->tree->getNodeForPath($sourcePath);
@@ -80,6 +88,38 @@ function beforeMove($sourcePath, $destinationPath) {
         }
     }
 
+    function beforeCopy($sourcePath, $destinationPath, $depth = null) {
+        $this->assertSameCalendarHome($sourcePath, $destinationPath);
+    }
+
+    /**
+     * SabreDAV runs COPY and MOVE through Tree::copy()/Tree::move(), which never emit
+     * calendarObjectChange and therefore skip the ORGANIZER validation a PUT goes through.
+     * Confining a transfer to a single calendar home keeps an event that a PUT would have
+     * rejected from being smuggled into someone else's calendar.
+     */
+    private function assertSameCalendarHome($sourcePath, $destinationPath): void {
+        $sourceHome = $this->calendarHomeOf($sourcePath);
+        $destinationHome = $this->calendarHomeOf($destinationPath);
+
+        // Not a calendar object on either end: collection level transfers are left to the ACL plugin.
+        if ($sourceHome === null || $destinationHome === null) return;
+
+        if ($sourceHome !== $destinationHome) {
+            throw new Forbidden('COPY and MOVE are only allowed within the same calendar home.');
+        }
+    }
+
+    private function calendarHomeOf($eventPath): ?string {
+        list($calendarPath,) = Utils::splitEventPath('/' . ltrim($eventPath, '/'));
+        if (!$calendarPath) {
+            return null;
+        }
+
+        // $calendarPath is 'calendars/{baseId}/{calendarUri}'.
+        return explode('/', $calendarPath)[1];
+    }
+
     private function validateCalendarOrganizer(VCalendar $calendar, $calendarPath, ?string $existingOrganizerUri = null): void {
         $vevents = $calendar->select('VEVENT');
         if (empty($vevents) || !($organizerUri = $this->extractOrganizerUri($vevents))) return;
diff --git a/run_test.sh b/run_test.sh
index 1c3879a5..6da96fd5 100755
--- a/run_test.sh
+++ b/run_test.sh
@@ -75,6 +75,7 @@ trap cleanup EXIT  # finally: sera exécuté *quoi qu'il arrive*
 javatest() {
     git clone https://github.com/linagora/twake-calendar-integration-tests.git it-tests ||  exit 1
     cd it-tests || exit 1
+    git checkout test-sabre-450 || exit 1
     bash pre-build.sh esn_sabre_test || exit 1
     mvn clean install -Dapi.version=1.43 -Dtest=com.linagora.dav.sabrev4_7.** -Damqp.scheduling.enabled=true || exit 1
 }