diff --git a/packages/hydrojudge/package.json b/packages/hydrojudge/package.json
index bfcf5f499..ebe1d22ac 100644
--- a/packages/hydrojudge/package.json
+++ b/packages/hydrojudge/package.json
@@ -1,7 +1,7 @@
 {
     "name": "@hydrooj/hydrojudge",
     "bin": "bin/hydrojudge.js",
-    "version": "3.0.1",
+    "version": "3.0.2",
     "main": "package.json",
     "author": "undefined <i@undefined.moe>",
     "repository": "https://github.com/hydro-dev/Hydro.git",
diff --git a/packages/hydrojudge/src/sandbox.ts b/packages/hydrojudge/src/sandbox.ts
index b2679e54d..fd655bf61 100644
--- a/packages/hydrojudge/src/sandbox.ts
+++ b/packages/hydrojudge/src/sandbox.ts
@@ -71,7 +71,7 @@ function parseArgs(execute: string): string[] {
 function proc(params: Parameter): Cmd {
     const copyOut = supportOptional
         ? params.copyOut
-        : params.copyOut.map((i) => (i.endsWith('?') ? i.substring(0, i.length - 1) : i));
+        : (params.copyOut || []).map((i) => (i.endsWith('?') ? i.substring(0, i.length - 1) : i));
     const size = parseMemoryMB(getConfig('stdio_size'));
     const rate = getConfig('rate');
     const copyOutCached = [...(params.copyOutCached || [])];