diff --git a/lib/Room.php b/lib/Room.php
index 18213c0a527..1e1a6565680 100644
--- a/lib/Room.php
+++ b/lib/Room.php
@@ -394,11 +394,12 @@ public function setParticipant(?string $userId, Participant $participant): void
 		$this->participant = $participant;
 	}
 
-	public function setActiveSince(\DateTime $since, int $callFlag): void {
-		if (!$this->activeSince) {
-			$this->activeSince = $since;
-		}
-		$this->callFlag |= $callFlag;
+	public function setActiveSince(?\DateTime $activeSince): void {
+		$this->activeSince = $activeSince;
+	}
+
+	public function setCallFlag(int $callFlag): void {
+		$this->callFlag = $callFlag;
 	}
 
 	public function getBreakoutRoomMode(): int {
diff --git a/lib/Service/RoomService.php b/lib/Service/RoomService.php
index d0352113bd6..f1ec619bca1 100644
--- a/lib/Service/RoomService.php
+++ b/lib/Service/RoomService.php
@@ -1202,7 +1202,7 @@ public function setActiveSince(Room $room, ?Participant $participant, \DateTime
 
 		if ($room->getActiveSince() instanceof \DateTime) {
 			// Call is already active, just someone upgrading the call flags
-			$room->setActiveSince($room->getActiveSince(), $callFlag);
+			$room->setCallFlag($callFlag);
 
 			$event = new RoomModifiedEvent($room, ARoomModifiedEvent::PROPERTY_IN_CALL, $callFlag, $oldCallFlag);
 			$this->dispatcher->dispatchTyped($event);
@@ -1217,7 +1217,8 @@ public function setActiveSince(Room $room, ?Participant $participant, \DateTime
 			->andWhere($update->expr()->isNull('active_since'));
 		$result = (bool)$update->executeStatement();
 
-		$room->setActiveSince($since, $callFlag);
+		$room->setActiveSince($since);
+		$room->setCallFlag($callFlag);
 
 		if (!$result) {
 			// Lost the race, someone else updated the database
diff --git a/tests/php/RoomTest.php b/tests/php/RoomTest.php
index e88a62c175e..f204ee761dc 100644
--- a/tests/php/RoomTest.php
+++ b/tests/php/RoomTest.php
@@ -67,4 +67,31 @@ public function testGetLobbyTimerIsPure(): void {
 		$this->assertEquals($timer, $room->getLobbyTimer());
 		$this->assertEquals($timer, $room->getLobbyTimer());
 	}
+
+	public function testSetActiveSinceSetsValue(): void {
+		$room = $this->createRoom();
+		$since = new \DateTime();
+		$room->setActiveSince($since);
+		$this->assertSame($since, $room->getActiveSince());
+	}
+
+	public function testSetActiveSinceAcceptsNull(): void {
+		$room = $this->createRoom();
+		$room->setActiveSince(new \DateTime());
+		$room->setActiveSince(null);
+		$this->assertNull($room->getActiveSince());
+	}
+
+	public function testSetCallFlagSetsValue(): void {
+		$room = $this->createRoom();
+		$room->setCallFlag(Participant::FLAG_WITH_VIDEO);
+		$this->assertSame(Participant::FLAG_WITH_VIDEO, $room->getCallFlag());
+	}
+
+	public function testSetCallFlagReplacesValue(): void {
+		$room = $this->createRoom();
+		$room->setCallFlag(Participant::FLAG_IN_CALL);
+		$room->setCallFlag(Participant::FLAG_WITH_VIDEO);
+		$this->assertSame(Participant::FLAG_WITH_VIDEO, $room->getCallFlag());
+	}
 }
diff --git a/tests/php/Service/RoomServiceTest.php b/tests/php/Service/RoomServiceTest.php
index f28fb51454b..68ed6290860 100644
--- a/tests/php/Service/RoomServiceTest.php
+++ b/tests/php/Service/RoomServiceTest.php
@@ -424,4 +424,59 @@ public function testVerifyPassword(): void {
 		$this->assertSame($verificationResult, ['result' => false, 'url' => 'https://test']);
 		$this->assertSame('passy', $room->getPassword());
 	}
+
+	public function testSetActiveSinceNoOpWhenFlagsUnchanged(): void {
+		$since = new \DateTime();
+		$room = $this->createMock(Room::class);
+		$room->method('getActiveSince')->willReturn($since);
+		$room->method('getCallFlag')->willReturn(Participant::FLAG_WITH_VIDEO);
+		$room->expects($this->never())->method('setActiveSince');
+		$room->expects($this->never())->method('setCallFlag');
+
+		$result = $this->service->setActiveSince($room, null, $since, Participant::FLAG_WITH_VIDEO, false);
+
+		$this->assertFalse($result);
+	}
+
+	public function testSetActiveSinceUpgradesCallFlagOnly(): void {
+		$since = new \DateTime();
+		$room = $this->createMock(Room::class);
+		$room->method('getActiveSince')->willReturn($since);
+		$room->method('getCallFlag')->willReturn(Participant::FLAG_IN_CALL);
+		$room->method('getId')->willReturn(0);
+		$room->expects($this->never())->method('setActiveSince');
+		$room->expects($this->once())->method('setCallFlag')
+			->with(Participant::FLAG_IN_CALL | Participant::FLAG_WITH_VIDEO);
+
+		$result = $this->service->setActiveSince($room, null, $since, Participant::FLAG_WITH_VIDEO, false);
+
+		$this->assertFalse($result);
+	}
+
+	public function testSetActiveSinceSetsActiveSinceAndCallFlagOnFreshCall(): void {
+		$since = new \DateTime();
+		$room = $this->createMock(Room::class);
+		$room->method('getActiveSince')->willReturn(null);
+		$room->method('getCallFlag')->willReturn(Participant::FLAG_DISCONNECTED);
+		$room->method('getId')->willReturn(0);
+		$room->expects($this->once())->method('setActiveSince')->with($since);
+		$room->expects($this->once())->method('setCallFlag')->with(Participant::FLAG_WITH_VIDEO);
+
+		$this->service->setActiveSince($room, null, $since, Participant::FLAG_WITH_VIDEO, false);
+	}
+
+	public function testSetActiveSinceMergesExistingFlagOnFreshCall(): void {
+		// Verifies that flag merging (previously $this->callFlag |= $callFlag in Room)
+		// is preserved after moving to $callFlag |= $oldCallFlag in RoomService.
+		$since = new \DateTime();
+		$room = $this->createMock(Room::class);
+		$room->method('getActiveSince')->willReturn(null);
+		$room->method('getCallFlag')->willReturn(Participant::FLAG_IN_CALL);
+		$room->method('getId')->willReturn(0);
+		$room->expects($this->once())->method('setActiveSince')->with($since);
+		$room->expects($this->once())->method('setCallFlag')
+			->with(Participant::FLAG_IN_CALL | Participant::FLAG_WITH_VIDEO);
+
+		$this->service->setActiveSince($room, null, $since, Participant::FLAG_WITH_VIDEO, false);
+	}
 }