diff --git a/packages/import-qduoj/index.ts b/packages/import-qduoj/index.ts
index 98f13939..8ce6ffcf 100644
--- a/packages/import-qduoj/index.ts
+++ b/packages/import-qduoj/index.ts
@@ -77,8 +77,12 @@ class ImportQduojHandler extends Handler {
                     });
                 }
                 if (+pdoc.display_id) pdoc.display_id = `P${pdoc.display_id}`;
-                const n = await ProblemModel.get(domainId, pdoc.display_id);
-                if (n) pdoc.display_id = null;
+                const isValidPid = async (id: string) => {
+                    if (!(/^[A-Za-z]+[0-9A-Za-z]*$/.test(id))) return false;
+                    if (await ProblemModel.get(domainId, id)) return false;
+                    return true;
+                };
+                if (!await isValidPid(pdoc.display_id)) pdoc.display_id = null;
                 const pid = await ProblemModel.add(
                     domainId, pdoc.display_id, pdoc.title, buildContent(content, 'html'),
                     this.user._id, pdoc.tags || [],
diff --git a/packages/import-qduoj/package.json b/packages/import-qduoj/package.json
index 10fe45ee..c31d5bf7 100644
--- a/packages/import-qduoj/package.json
+++ b/packages/import-qduoj/package.json
@@ -1,6 +1,6 @@
 {
     "name": "@hydrooj/import-qduoj",
-    "version": "1.5.3",
+    "version": "1.5.4",
     "description": "Import QDUOJ problem export",
     "main": "index.ts",
     "repository": "https://github.com/hydro-dev/Hydro.git",