diff --git a/djangoproject/templates/search_form.html b/djangoproject/templates/search_form.html
index 65823c757..eea6c3717 100644
--- a/djangoproject/templates/search_form.html
+++ b/djangoproject/templates/search_form.html
@@ -3,6 +3,7 @@
   <form action="{% url 'document-search' version=version lang=lang host 'docs' %}">
     <label id="docs-search-label" class="visuallyhidden" for="{{ form.q.id_for_label }}">{{ form.q.field.widget.attrs.placeholder }}</label>
     {{ form.q }}
+    <input type="hidden" name="category" value="{{ active_category }}">
 
     <button type="submit">
       <i class="icon icon-search" aria-hidden="true"></i>
diff --git a/docs/templatetags/docs.py b/docs/templatetags/docs.py
index 012ca9478..0f2157f37 100644
--- a/docs/templatetags/docs.py
+++ b/docs/templatetags/docs.py
@@ -34,6 +34,7 @@ def search_form(context):
 
     request = context["request"]
     lang = context.get("lang", settings.DEFAULT_LANGUAGE_CODE)
+    active_category = context.get("active_category", "")
 
     if "version" in context:
         release = DocumentRelease.objects.select_related(
@@ -46,6 +47,7 @@ def search_form(context):
         "form": DocSearchForm(request.GET, release=release),
         "version": release.version,
         "lang": lang,
+        "active_category": active_category,
     }
 
 
diff --git a/docs/tests/test_views.py b/docs/tests/test_views.py
index d811ddfec..a759793ba 100644
--- a/docs/tests/test_views.py
+++ b/docs/tests/test_views.py
@@ -164,6 +164,31 @@ def test_search_website_category_french(self):
             html=True,
         )
 
+    def test_search_category_filter_preserved(self):
+        response = self.client.get(
+            "/en/5.1/search/?q=potato&category=ref",
+            headers={"host": "docs.djangoproject.localhost:8000"},
+        )
+        self.assertEqual(response.status_code, 200)
+        self.assertContains(
+            response, '<input type="hidden" name="category" value="ref">'
+        )
+        self.assertContains(
+            response, f"{self.active_filter}API Reference</a>", html=True
+        )
+        response = self.client.post(
+            "/en/5.1/search/?q=potato&category=ref",
+            headers={"host": "docs.djangoproject.localhost:8000"},
+            data={"category": "ref", "q": "fish"},
+        )
+        self.assertEqual(response.status_code, 200)
+        self.assertContains(
+            response, '<input type="hidden" name="category" value="ref">'
+        )
+        self.assertContains(
+            response, f"{self.active_filter}API Reference</a>", html=True
+        )
+
     def test_code_links(self):
         queryset_data = {
             "metadata": {
diff --git a/docs/views.py b/docs/views.py
index a525b3c1d..f86f75063 100644
--- a/docs/views.py
+++ b/docs/views.py
@@ -144,6 +144,7 @@ def search_results(request, lang, version, per_page=10, orphans=3):
 
     activate(lang)
 
+    doc_category = DocumentationCategory.parse(request.GET.get("category"))
     form = DocSearchForm(request.GET or None, release=release)
 
     # Get available languages for the language switcher
@@ -158,6 +159,7 @@ def search_results(request, lang, version, per_page=10, orphans=3):
         "release": release,
         "available_languages": available_languages,
         "searchparams": request.GET.urlencode(),
+        "active_category": doc_category or "",
     }
 
     if form.is_valid():
@@ -169,7 +171,6 @@ def search_results(request, lang, version, per_page=10, orphans=3):
             if exact is not None:
                 return redirect(exact)
 
-            doc_category = DocumentationCategory.parse(request.GET.get("category"))
             results = Document.objects.search(
                 q, release, document_category=doc_category
             )
@@ -201,7 +202,6 @@ def search_results(request, lang, version, per_page=10, orphans=3):
                     "page": page,
                     "paginator": paginator,
                     "start_sel": START_SEL,
-                    "active_category": doc_category,
                     "DocumentationCategory": DocumentationCategory,
                 }
             )