diff --git a/packages/hydrooj/src/handler/problem.ts b/packages/hydrooj/src/handler/problem.ts
index 6b4c9aefa..6cf7bfabe 100644
--- a/packages/hydrooj/src/handler/problem.ts
+++ b/packages/hydrooj/src/handler/problem.ts
@@ -170,15 +170,17 @@ export class ProblemMainHandler extends Handler {
                 pdocs.map((i) => i.docId),
             ));
         }
+        let qs = sortStrategy !== 'default' ? `sort=${sortStrategy}` : '';
+        if (q) qs += `${qs ? '&' : ''}q=${encodeURIComponent(q)}`;
         if (pjax) {
             this.response.body = {
                 title: this.renderTitle(this.translate('problem_main')),
                 fragments: (await Promise.all([
                     this.renderHTML('partials/problem_list.html', {
-                        page, ppcount, pcount, pdocs, psdict, qs: q, sort: sortStrategy,
+                        page, ppcount, pcount, pdocs, psdict, qs, q, sort: sortStrategy,
                     }),
                     this.renderHTML('partials/problem_stat.html', { pcount, pcountRelation: this.queryContext.pcountRelation }),
-                    this.renderHTML('partials/problem_lucky.html', { qs: q }),
+                    this.renderHTML('partials/problem_lucky.html', { q }),
                 ])).map((i) => ({ html: i })),
             };
         } else {
@@ -189,7 +191,8 @@ export class ProblemMainHandler extends Handler {
                 pcountRelation: this.queryContext.pcountRelation,
                 pdocs,
                 psdict,
-                qs: q,
+                qs,
+                q,
                 sort: sortStrategy,
             };
         }
diff --git a/packages/ui-default/templates/partials/problem_list.html b/packages/ui-default/templates/partials/problem_list.html
index 259cc4df9..fcd743150 100644
--- a/packages/ui-default/templates/partials/problem_list.html
+++ b/packages/ui-default/templates/partials/problem_list.html
@@ -6,7 +6,7 @@
 {% if not pdocs.length %}
   {{ nothing.render('Sorry, there are no problems in the problem set.') }}
 {% else %}
-  {{ paginator.render(page, ppcount, position='top', add_qs=('q=' + qs if qs else '')) }}
+  {{ paginator.render(page, ppcount, position='top', add_qs=qs) }}
   <table class="data-table hide-problem-tag">
     <colgroup>
       <col class="col--checkbox display-mode-hide">
@@ -63,6 +63,6 @@
     {%- endfor -%}
     </tbody>
   </table>
-  {{ paginator.render(page, ppcount, add_qs=('q=' + qs if qs else '')) }}
+  {{ paginator.render(page, ppcount, add_qs=qs) }}
 {% endif %}
 </div>
diff --git a/packages/ui-default/templates/partials/problem_lucky.html b/packages/ui-default/templates/partials/problem_lucky.html
index bc127a6b1..5b0aa7594 100644
--- a/packages/ui-default/templates/partials/problem_lucky.html
+++ b/packages/ui-default/templates/partials/problem_lucky.html
@@ -1,6 +1,6 @@
 <div data-fragment-id="problem_lucky">
   <p>
-    <a href="{{ url('problem_random', query={q:qs}) if qs else url('problem_random') }}" class="expanded button" target="_blank">
+    <a href="{{ url('problem_random', query={q:q}) if q else url('problem_random') }}" class="expanded button" target="_blank">
       <span class="icon icon-feeling-lucky"></span> {{ _('Lucky') }}
     </a>
   </p>
diff --git a/packages/ui-default/templates/problem_main.html b/packages/ui-default/templates/problem_main.html
index 29e183bbd..547c18dc4 100644
--- a/packages/ui-default/templates/problem_main.html
+++ b/packages/ui-default/templates/problem_main.html
@@ -8,7 +8,7 @@
         <div class="section__body no-padding">
           <form method="get" id="searchForm" action="{{ url('problem_main') }}">
             <div class="search">
-              <input name="q" type="text" value="{{ qs }}" placeholder="{{ _('Search') }}">
+              <input name="q" type="text" value="{{ q }}" placeholder="{{ _('Search') }}">
               {% include "partials/problem_stat.html" %}
               <select name="sort" class="search-sort">
                 {%- for sortType in ["default", "recent"] -%}