diff --git a/.github/workflows/pkg_test.yml b/.github/workflows/pkg_test.yml
index 45a4a00c..60512e62 100644
--- a/.github/workflows/pkg_test.yml
+++ b/.github/workflows/pkg_test.yml
@@ -7,13 +7,16 @@ jobs:
     runs-on: "ubuntu-20.04"
     container: debian:10
     steps:
+      - name: Change Owner of Container Working Directory
+        run: chown root:root .
+
       - name: Install git
         run: |
           apt-get update -q
           apt-get install -y git
 
       - name: Check out repository code
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
         with:
           fetch-depth: 0
 
diff --git a/newapi/debian/changelog b/newapi/debian/changelog
index a24ec779..e45f1895 100644
--- a/newapi/debian/changelog
+++ b/newapi/debian/changelog
@@ -1,3 +1,9 @@
+ooni-api (1.0.35) unstable; urgency=medium
+
+  * Add feature flagging
+
+ -- Federico Ceratto <federico@debian.org>  Mon, 09 Jan 2023 17:41:05 +0000
+
 ooni-api (1.0.34) unstable; urgency=medium
 
   * Implement MAT granularity
diff --git a/newapi/ooniapi/probe_services.py b/newapi/ooniapi/probe_services.py
index 15559a41..a996ce3c 100644
--- a/newapi/ooniapi/probe_services.py
+++ b/newapi/ooniapi/probe_services.py
@@ -176,6 +176,7 @@ def check_in() -> Response:
           properties:
             v:
               type: integer
+              description: response format version
             probe_cc:
               type: string
               description: probe CC inferred from GeoIP or ZZ
@@ -188,8 +189,19 @@ def check_in() -> Response:
             utc_time:
               type: string
               description: current UTC time as YYYY-mm-ddTHH:MM:SSZ
+            conf:
+              type: object
+              description: auxiliary configuration parameters
+              psiphon:
+                type: object
+              tor:
+                type: object
+              features:
+                type: object
+                description: feature flags
             tests:
               type: object
+              description: test-specific configuration
               properties:
                 web_connectivity:
                   type: object
@@ -256,10 +268,19 @@ def check_in() -> Response:
     try:
         torconf = _load_json(current_app.config["TOR_TARGETS_CONFFILE"])
         psconf = _load_json(current_app.config["PSIPHON_CONFFILE"])
-        conf = dict(tor=torconf, psiphon=psconf)
+        conf = dict(tor=torconf, psiphon=psconf, features={})
     except Exception as e:
         log.error(str(e), exc_info=True)
-        conf = {}
+        conf = dict(features={})
+
+    try:
+        # set webconnectivity_0.5 feature flag for some probes
+        ipaddr = extract_probe_ipaddr()
+        n = int(ipaddr.split(".", 2)[1])
+        if n in (34,):
+            conf["features"]["webconnectivity_0.5"] = True
+    except Exception:
+        pass
 
     resp["tests"] = {
         "web_connectivity": {"urls": test_items},
diff --git a/newapi/tests/integ/test_probe_services.py b/newapi/tests/integ/test_probe_services.py
index 23a4cfb7..59e39ad5 100644
--- a/newapi/tests/integ/test_probe_services.py
+++ b/newapi/tests/integ/test_probe_services.py
@@ -102,7 +102,7 @@ def test_check_in_basic(client):
     assert cc == "US"
 
     # psiphon and tor configurations
-    assert sorted(c["conf"]) == ["psiphon", "tor"]
+    assert sorted(c["conf"]) == ["features", "psiphon", "tor"]
 
 
 def test_check_in_url_category_news(client):
diff --git a/newapi/tests/integ/test_probe_services_nodb.py b/newapi/tests/integ/test_probe_services_nodb.py
index d48948e3..829aa070 100644
--- a/newapi/tests/integ/test_probe_services_nodb.py
+++ b/newapi/tests/integ/test_probe_services_nodb.py
@@ -148,7 +148,7 @@ def test_check_in(client, mocks):
     assert cc == "US"
 
     # psiphon and tor configurations
-    assert sorted(c["conf"]) == ["psiphon", "tor"]
+    assert sorted(c["conf"]) == ["features", "psiphon", "tor"]
 
 
 def test_check_in_url_category_news(client, mocks):