diff --git a/api/debian/changelog b/api/debian/changelog
index a13f205a..c8a58722 100644
--- a/api/debian/changelog
+++ b/api/debian/changelog
@@ -1,3 +1,9 @@
+ooni-api (1.0.89) unstable; urgency=medium
+
+  * Start preparing for WebConnectivity v0.4 vs v0.5 A/B testing
+
+ -- Simone Basso <simone@ooni.org>  Tue, 20 Feb 2024 10:34:00 +0100
+
 ooni-api (1.0.88) unstable; urgency=medium
 
   * Add more logging
diff --git a/api/ooniapi/probe_services.py b/api/ooniapi/probe_services.py
index 49f1a3be..a5aa02b1 100644
--- a/api/ooniapi/probe_services.py
+++ b/api/ooniapi/probe_services.py
@@ -11,6 +11,7 @@
 from urllib.request import urlopen
 import ipaddress
 import time
+import os
 
 import ujson
 from flask import Blueprint, current_app, request, Response
@@ -275,9 +276,15 @@ def check_in() -> Response:
         features={"torsf_enabled": True, "vanilla_tor_enabled": True}
     )
 
-    # set webconnectivity_0.5 feature flag for some probes
-    octect = extract_probe_ipaddr_octect(1, 0)
-    if octect in (34, 239):
+    # WebConnectivity v0.4 vs v0.5 A/B testing. Try to avoid using the new version of
+    # the experiment in Cambodia and Belarus where there are upcoming elections.
+    #
+    # See https://github.com/ooni/probe/issues/2555#issuecomment-1906097413.
+    if (
+        probe_cc not in ("BY", "KH") and
+        software_name == "ooniprobe-android-unattended" and
+        software_version == "3.8.6"
+      ):
         conf["features"]["webconnectivity_0.5"] = True
 
     conf["test_helpers"] = generate_test_helpers_conf()
diff --git a/api/tests/integ/test_probe_services_nodb.py b/api/tests/integ/test_probe_services_nodb.py
index c159660f..d772e9ab 100644
--- a/api/tests/integ/test_probe_services_nodb.py
+++ b/api/tests/integ/test_probe_services_nodb.py
@@ -246,6 +246,56 @@ def test_check_in_geoip(client, mocks):
     assert c["probe_network_name"] is not None
 
 
+# See https://github.com/ooni/probe/issues/2555 for context. Delete when the A/B testing is done.
+def test_check_in_abtesting_2555(client, mocks):
+    testcases = [{
+        "name": "when the country is KH and the software name and version would match",
+        "inputs": {
+            "probe_cc": "KH",
+            "software_name": "ooniprobe-android-unattended",
+            "software_version": "3.8.6",
+        },
+        "expect": False,
+    }, {
+        "name": "when the country is BY and the software name and version would match",
+        "inputs": {
+            "probe_cc": "BY",
+            "software_name": "ooniprobe-android-unattended",
+            "software_version": "3.8.6",
+        },
+        "expect": False,
+    }, {
+        "name": "when the country is neither BY nor KH with unexpected software_name",
+        "inputs": {
+            "probe_cc": "IT",
+            "software_name": "ooniprobe-android",
+            "software_version": "3.8.6",
+        },
+        "expect": False,
+    }, {
+        "name": "when the country is neither BY nor KH with unexpected software_version",
+        "inputs": {
+            "probe_cc": "IT",
+            "software_name": "ooniprobe-android-unattended",
+            "software_version": "3.8.4",
+        },
+        "expect": False,
+    }, {
+        "name": "when the country is neither BY nor KH with correct software_version and software_version",
+        "inputs": {
+            "probe_cc": "IT",
+            "software_name": "ooniprobe-android-unattended",
+            "software_version": "3.8.6",
+        },
+        "expect": True,
+    }]
+    for tc in testcases:
+        print("running", tc["name"])
+        j = tc["inputs"]
+        c = client.post("/api/v1/check-in", json=j).json
+        assert c.get("conf", {}).get("features", {}).get("webconnectivity_0.5", False) == tc["expect"]
+
+
 # # Test /api/v1/collectors