diff --git a/readthedocs/proxito/tests/test_hosting.py b/readthedocs/proxito/tests/test_hosting.py
index ee1d53f6d83..f35f2004d8d 100644
--- a/readthedocs/proxito/tests/test_hosting.py
+++ b/readthedocs/proxito/tests/test_hosting.py
@@ -384,6 +384,18 @@ def test_flyout_single_version_project(self):
         self.version.has_htmlzip = True
         self.version.save()
 
+        # Add extra built and active versions to emulate a project that went
+        # from multiple versions to single version.
+        # These versions shouldn't be included in the `versions.active` field.
+        for i in range(5):
+            fixture.get(
+                Version,
+                privacy_level=PUBLIC,
+                active=True,
+                built=True,
+                project=self.project,
+            )
+
         self.project.versioning_scheme = SINGLE_VERSION_WITHOUT_TRANSLATIONS
         self.project.save()
 
@@ -400,9 +412,8 @@ def test_flyout_single_version_project(self):
             },
         )
         assert r.status_code == 200
-
-        expected = []
-        assert r.json()["versions"]["active"] == expected
+        expected = ["latest"]
+        assert [v["slug"] for v in r.json()["versions"]["active"]] == expected
 
         expected = {
             "pdf": "https://project.dev.readthedocs.io/_/downloads/en/latest/pdf/",
diff --git a/readthedocs/proxito/views/hosting.py b/readthedocs/proxito/views/hosting.py
index 370e2e4a0c8..108fe7f344d 100644
--- a/readthedocs/proxito/views/hosting.py
+++ b/readthedocs/proxito/views/hosting.py
@@ -342,14 +342,21 @@ def _v1(self, project, version, build, filename, url, request):
         # projects that don't have one already
         AddonsConfig.objects.get_or_create(project=project)
 
-        if project.supports_multiple_versions:
-            versions_active_built_not_hidden = (
-                self._get_versions(request, project)
-                .select_related("project")
-                .order_by("-slug")
+        versions_active_built_not_hidden = (
+            self._get_versions(request, project)
+            .select_related("project")
+            .order_by("-slug")
+        )
+        sorted_versions_active_built_not_hidden = versions_active_built_not_hidden
+        if not project.supports_multiple_versions:
+            # Return only one version when the project doesn't support multiple versions.
+            # That version is the only one the project serves.
+            sorted_versions_active_built_not_hidden = (
+                sorted_versions_active_built_not_hidden.filter(
+                    slug=project.get_default_version()
+                )
             )
-            sorted_versions_active_built_not_hidden = versions_active_built_not_hidden
-
+        else:
             if (
                 project.addons.flyout_sorting
                 == ADDONS_FLYOUT_SORTING_SEMVER_READTHEDOCS_COMPATIBLE