diff --git a/src/docker.ts b/src/docker.ts
index 87794f9..ffb5cb4 100644
--- a/src/docker.ts
+++ b/src/docker.ts
@@ -215,7 +215,11 @@ function stderrStreamToString(stream: NodeJS.WritableStream): Promise<string> {
   return new Promise((resolve, reject) => {
     stream.on('data', (chunk) => chunks.push(Buffer.from(chunk)));
     stream.on('error', (err) => reject(err));
-    stream.on('end', () => resolve(Buffer.concat(chunks).toString('utf8')));
+    stream.on('end', () =>
+      resolve(
+        Buffer.concat(chunks.map((x) => Uint8Array.from(x))).toString('utf8'),
+      ),
+    );
   });
 }