diff --git a/packages/hydrooj/src/service/watcher.ts b/packages/hydrooj/src/service/watcher.ts
index 951550cbb..2d17023d5 100644
--- a/packages/hydrooj/src/service/watcher.ts
+++ b/packages/hydrooj/src/service/watcher.ts
@@ -152,10 +152,11 @@ export default class Watcher extends Service {
         for (const filename in require.cache) {
             const module = require.cache[filename];
             const plugin = unwrapExports(module.exports);
+            if (!(typeof plugin === 'object' && 'apply' in plugin)) continue;
             const runtime = this.ctx.registry.get(plugin);
             if (!runtime || this.declined.has(filename)) continue;
             pending.set(filename, runtime);
-            if (!plugin?.['sideEffect']) this.declined.add(filename);
+            if (!(plugin && 'sideEffect' in plugin && plugin['sideEffect'])) this.declined.add(filename);
         }
 
         for (const [filename, runtime] of pending) {