diff --git a/cli/src/index.js b/cli/src/index.js
index d7c97eda..390dc43d 100644
--- a/cli/src/index.js
+++ b/cli/src/index.js
@@ -183,31 +183,36 @@ function progressTracker(results) {
   return tracker;
 }
 
-async function checkInputFilesValid(files) {
+async function getInputFiles(paths) {
   const validFiles = [];
 
-  for (const file of files) {
-    try {
-      await fsp.stat(file);
-    } catch (err) {
-      if (err.code === 'ENOENT') {
-        console.warn(
-          `Warning: Input file does not exist: ${resolvePath(file)}`,
-        );
-        continue;
-      } else {
-        throw err;
+  for (const path of paths) {
+    const files = (await fsp.lstat(path)).isDirectory()
+      ? (await fsp.readdir(path)).map(file => join(path, file))
+      : [path];
+    for (const file of files) {
+      try {
+        await fsp.stat(file);
+      } catch (err) {
+        if (err.code === 'ENOENT') {
+          console.warn(
+            `Warning: Input file does not exist: ${resolvePath(file)}`,
+          );
+          continue;
+        } else {
+          throw err;
+        }
       }
-    }
 
-    validFiles.push(file);
+      validFiles.push(file);
+    }
   }
 
   return validFiles;
 }
 
 async function processFiles(files) {
-  files = await checkInputFilesValid(files);
+  files = await getInputFiles(files);
 
   const parallelism = cpus().length;
 
diff --git a/cli/src/worker_pool.js b/cli/src/worker_pool.js
index 90830f5d..57ebbfa7 100644
--- a/cli/src/worker_pool.js
+++ b/cli/src/worker_pool.js
@@ -24,7 +24,7 @@ function jobPromise(worker, msg) {
 
 export default class WorkerPool {
   constructor(numWorkers, workerFile) {
-    this.closing = false;
+    this.numWorkers = numWorkers;
     this.jobQueue = new TransformStream();
     this.workerQueue = new TransformStream();
 
@@ -42,7 +42,6 @@ export default class WorkerPool {
     while (true) {
       const { value, done } = await reader.read();
       if (done) {
-        this.workerQueue.writable.close();
         await this._terminateAll();
         return;
       }
@@ -50,12 +49,6 @@ export default class WorkerPool {
       const worker = await this._nextWorker();
       jobPromise(worker, msg).then((result) => {
         resolve(result);
-        // If we are in the process of closing, `workerQueue` is
-        // already closed and we can’t requeue the worker.
-        if (this.closing) {
-          worker.terminate();
-          return;
-        }
         const writer = this.workerQueue.writable.getWriter();
         writer.write(worker);
         writer.releaseLock();
@@ -71,18 +64,15 @@ export default class WorkerPool {
   }
 
   async _terminateAll() {
-    while (true) {
+    for (let n = 0; n < this.numWorkers; n++) {
       const worker = await this._nextWorker();
-      if (!worker) {
-        return;
-      }
       worker.terminate();
     }
+    this.workerQueue.writable.close();
   }
 
   async join() {
-    this.closing = true;
-    this.jobQueue.writable.close();
+    this.jobQueue.writable.getWriter().close();
     await this.done;
   }