diff --git a/build/psalm-baseline.xml b/build/psalm-baseline.xml
index 23021eb80b808..fae69bf6fa0f9 100644
--- a/build/psalm-baseline.xml
+++ b/build/psalm-baseline.xml
@@ -3164,15 +3164,8 @@
   <file src="lib/private/Preview/Generator.php">
     <InvalidArgument>
       <code>$maxPreviewImage</code>
-      <code>$semId</code>
       <code>IPreview::EVENT</code>
     </InvalidArgument>
-    <InvalidReturnStatement>
-      <code>$sem</code>
-    </InvalidReturnStatement>
-    <InvalidReturnType>
-      <code>false|resource</code>
-    </InvalidReturnType>
     <MismatchingDocblockParamType>
       <code>ISimpleFile</code>
     </MismatchingDocblockParamType>
diff --git a/lib/private/Preview/Generator.php b/lib/private/Preview/Generator.php
index d75d9c84cd284..c83cdb96e2719 100644
--- a/lib/private/Preview/Generator.php
+++ b/lib/private/Preview/Generator.php
@@ -227,7 +227,7 @@ public function generatePreviews(File $file, array $specifications, $mimeType =
 	 *
 	 * @param int $semId
 	 * @param int $concurrency
-	 * @return false|resource the semaphore on success or false on failure
+	 * @return false|\SysvSemaphore the semaphore on success or false on failure
 	 */
 	public static function guardWithSemaphore(int $semId, int $concurrency) {
 		if (!extension_loaded('sysvsem')) {
@@ -246,11 +246,11 @@ public static function guardWithSemaphore(int $semId, int $concurrency) {
 	/**
 	 * Releases the semaphore acquired from {@see Generator::guardWithSemaphore()}.
 	 *
-	 * @param resource|bool $semId the semaphore identifier returned by guardWithSemaphore
+	 * @param false|\SysvSemaphore $semId the semaphore identifier returned by guardWithSemaphore
 	 * @return bool
 	 */
-	public static function unguardWithSemaphore($semId): bool {
-		if (!is_resource($semId) || !extension_loaded('sysvsem')) {
+	public static function unguardWithSemaphore(false|\SysvSemaphore $semId): bool {
+		if ($semId === false || !($semId instanceof \SysvSemaphore)) {
 			return false;
 		}
 		return sem_release($semId);