diff --git a/readthedocs/proxito/tests/test_hosting.py b/readthedocs/proxito/tests/test_hosting.py
index fd41467fc6b..9b23e28cda1 100644
--- a/readthedocs/proxito/tests/test_hosting.py
+++ b/readthedocs/proxito/tests/test_hosting.py
@@ -89,10 +89,17 @@ def _get_response_dict(self, view_name, filepath=None):
         return json.load(open(filename))
 
     def _normalize_datetime_fields(self, obj):
-        obj["projects"]["current"]["created"] = "2019-04-29T10:00:00Z"
-        obj["projects"]["current"]["modified"] = "2019-04-29T12:00:00Z"
-        obj["builds"]["current"]["created"] = "2019-04-29T10:00:00Z"
-        obj["builds"]["current"]["finished"] = "2019-04-29T10:01:00Z"
+        try:
+            obj["projects"]["current"]["created"] = "2019-04-29T10:00:00Z"
+            obj["projects"]["current"]["modified"] = "2019-04-29T12:00:00Z"
+        except:
+            pass
+
+        try:
+            obj["builds"]["current"]["created"] = "2019-04-29T10:00:00Z"
+            obj["builds"]["current"]["finished"] = "2019-04-29T10:01:00Z"
+        except:
+            pass
         return obj
 
     def test_get_config_v1(self):
@@ -727,6 +734,33 @@ def test_send_project_version_slugs_and_url(self):
             "v1"
         )
 
+    def test_send_project_slug_and_notfound_version_slug(self):
+        r = self.client.get(
+            reverse("proxito_readthedocs_docs_addons"),
+            {
+                "api-version": "1.0.0",
+                "client-version": "0.6.0",
+                "project-slug": self.project.slug,
+                "version-slug": "not-found",
+            },
+            secure=True,
+            headers={
+                "host": "project.dev.readthedocs.io",
+            },
+        )
+        assert r.status_code == 200
+
+        expected_response = self._get_response_dict("v1")
+
+        # Since there is no version, there are some fields that we need to change from the default response
+        del expected_response["addons"]["doc_diff"]
+        expected_response["builds"]["current"] = None
+        expected_response["versions"]["current"] = None
+        expected_response["readthedocs"]["resolver"]["filename"] = None
+        expected_response["addons"]["search"]["default_filter"] = f"project:{self.project.slug}"
+        assert self._normalize_datetime_fields(r.json()) == expected_response
+
+
     def test_custom_domain_url(self):
         fixture.get(
             Domain,
diff --git a/readthedocs/proxito/views/hosting.py b/readthedocs/proxito/views/hosting.py
index 8ca93564467..513fcc99e89 100644
--- a/readthedocs/proxito/views/hosting.py
+++ b/readthedocs/proxito/views/hosting.py
@@ -134,7 +134,10 @@ def _resolve_resources(self):
         else:
             # When not sending "url", we require "project-slug" and "version-slug".
             project = get_object_or_404(Project, slug=project_slug)
-            version = get_object_or_404(project.versions.all(), slug=version_slug)
+            # We do allow hitting this URL without a valid version.
+            # This is the same case than sending `?url=` with a partial match
+            # (eg. invalid URL path).
+            version = project.versions.filter(slug=version_slug).first()
 
         # A project is always required.
         if not project:
@@ -378,6 +381,10 @@ def _v1(self, project, version, build, filename, url, request):
                     project.addons.flyout_sorting_latest_stable_at_beginning,
                 )
 
+        search_default_filter = f"project:{project.slug}"
+        if version:
+            search_default_filter = f"project:{project.slug}/{version.slug}"
+
         data = {
             "api_version": "1",
             "projects": self._get_projects_response(
@@ -478,7 +485,7 @@ def _v1(self, project, version, build, filename, url, request):
                         #     f"subprojects:{project.slug}/{version.slug}",
                         # ],
                     ],
-                    "default_filter": f"project:{project.slug}/{version.slug}" if version else None,
+                    "default_filter": search_default_filter,
                 },
                 "linkpreviews": {
                     "enabled": project.addons.linkpreviews_enabled,