diff --git a/index.js b/index.js
index 28337f6..dbd3b25 100644
--- a/index.js
+++ b/index.js
@@ -430,7 +430,7 @@ async function fastifyStatic (fastify, opts) {
       const files = globSync('**/**', {
         cwd: rootPath, absolute: true, follow: true, nodir: true, dot: opts.serveDotFiles, ignore: opts.hashSkip
       })
-      const hashQueue = fastq.promise(generateFileHash, os.availableParallelism)
+      const hashQueue = fastq.promise(generateFileHash, os.availableParallelism())
       const hashPromises = files.map((file) => hashQueue.push(file))
       const hashes = await Promise.all(hashPromises)
 
diff --git a/lib/dirList.js b/lib/dirList.js
index 5681ec9..0205d33 100644
--- a/lib/dirList.js
+++ b/lib/dirList.js
@@ -41,7 +41,7 @@ const dirList = {
       }
     }
 
-    const queue = fastq.promise(worker, os.availableParallelism)
+    const queue = fastq.promise(worker, os.availableParallelism())
     await Promise.all(files.map(filename => queue.push(filename)))
 
     async function getExtendedInfo (folderPath) {