diff --git a/checksums/SHA256SUMS b/checksums/SHA256SUMS
index 9d49246..1786850 100644
--- a/checksums/SHA256SUMS
+++ b/checksums/SHA256SUMS
@@ -16,14 +16,14 @@ d7d2fd7ab651d1f2f026bdb11d62e2c0c6ce6ee3128c9814d09550cf4304b3f2  ocf/loxthelion
 70431e0d390a3612339c7b5887286c1be4d6b305cbe8898e7895a211c26b6087  ocf/loxthelion/managed-container.d/engine.sh
 6c92c095ce10ac95d843fdc1c49e31c19491ca22fdac960affd8649606d76d82  ocf/loxthelion/managed-container.d/lifecycles/systemd.sh
 5f3528932ea72ef42c18465e7f31f9a430407e8d4ff7c03c705fe8cae39dc26e  ocf/loxthelion/managed-container.d/proxy.sh
-fb01359a84062ec3e910a8b27e460953a0ae1641a69167b3497f2594911d2a00  ocf/loxthelion/managed-container.d/proxy_client.py
+1acc1776f521557a047e7a53e5253f3b4373e9269cb3d9c5872b3e48033d2c18  ocf/loxthelion/managed-container.d/proxy_client.py
 f82e2571d309bce8e4d7e6aee6b61b68feb7d99dc85bb8b688b6123c13ccf6a7  ocf/loxthelion/managed-container.d/runtimes/podman.sh
 4a99efea3d4a185e0630db89cfacc28aa8777bad9c747794ae69f70d87cd0327  pacemaker/README.md
 a42bb59a058ffeb59c1baa96e403856910bbbaea98f9104ff93daf4b5970c780  postgres-host/postgres-ha-bootstrap
 957a5a72ed277d0216e070abb80733483be3d421b9fa488e27fdd75bb2919548  postgres-host/postgres-ha-peer-config.sh
 deb09e3ae40629f43b262ba4f9a7ebf59a1dca3da9d8c94478f670aea28bd0e1  quadlet/postgres.container
 04a125068677bbee6e71d313ca9d95d35faa32851b79de781cd7b9f466561445  quadlet/postgres.env.example
-0fb32ab5a9a51044ae9e4ae75b7d70bfb7f5e640c41a3d0de02277c9a8c44c91  tests/run-all.sh
+82162526c92a18c90ee425a28a89667fc211c7be4825ef2e91747e97efca41bd  tests/run-all.sh
 5e5d4fdd2b6c7e0b8b146de7aad06c1f96b221a10fec525b00d40e0d85709fb0  tests/test-entrypoint-structure.sh
 b83f0415c09f0be34c51722370e5b07c51b9a9756d305d3b3f50827f484aa4dd  tests/test-proxy-client-actions.py
 c3b988d7b2b1b138bb2530df9172f96bb0f5edc2f1561f38f0055695f4126134  tests/test-proxy-protocol.sh
diff --git a/ocf/loxthelion/managed-container.d/proxy_client.py b/ocf/loxthelion/managed-container.d/proxy_client.py
index 659b1ad..382af58 100755
--- a/ocf/loxthelion/managed-container.d/proxy_client.py
+++ b/ocf/loxthelion/managed-container.d/proxy_client.py
@@ -17,13 +17,21 @@ class ProtocolFailure(Exception):
     pass
 
 
-def send_request(socket_path, resource, action):
+def send_request(
+    socket_path,
+    resource,
+    action,
+    parameters=None,
+):
     request = {
         "protocol_version": PROTOCOL_VERSION,
         "action": action,
         "resource": resource,
     }
 
+    if parameters is not None:
+        request["parameters"] = parameters
+
     try:
         sock = socket.socket(
             socket.AF_UNIX,
@@ -166,12 +174,26 @@ def format_result(action, result):
 
 
 def main():
-    if len(sys.argv) != 6:
+    if len(sys.argv) not in (6, 7):
         raise SystemExit(11)
 
     socket_path = sys.argv[1]
     resource = sys.argv[2]
     action = sys.argv[3]
+    request_parameters = None
+
+    if len(sys.argv) == 7:
+        try:
+            request_parameters = json.loads(sys.argv[6])
+
+        except (
+            TypeError,
+            json.JSONDecodeError,
+        ):
+            raise SystemExit(11)
+
+        if not isinstance(request_parameters, dict):
+            raise SystemExit(11)
 
     try:
         transport_failure = int(sys.argv[4])
@@ -188,6 +210,7 @@ def main():
             socket_path,
             resource,
             action,
+            request_parameters,
         )
 
     except TransportFailure:
diff --git a/tests/run-all.sh b/tests/run-all.sh
index abf639d..ff6fa2d 100755
--- a/tests/run-all.sh
+++ b/tests/run-all.sh
@@ -23,6 +23,7 @@ echo ">>> Proxy protocol contract"
 echo
 echo ">>> Generic proxy client actions"
 python3 ./tests/test-proxy-client-actions.py
+python3 ./tests/test-proxy-client-parameters.py
 
 echo
 echo ">>> Python syntax"
diff --git a/tests/test-proxy-client-parameters.py b/tests/test-proxy-client-parameters.py
new file mode 100755
index 0000000..6e929fe
--- /dev/null
+++ b/tests/test-proxy-client-parameters.py
@@ -0,0 +1,84 @@
+#!/usr/bin/env python3
+
+import importlib.util
+import json
+import socket
+import tempfile
+import threading
+from pathlib import Path
+
+
+CLIENT_PATH = Path(
+    "ocf/loxthelion/managed-container.d/proxy_client.py"
+)
+
+spec = importlib.util.spec_from_file_location(
+    "proxy_client",
+    CLIENT_PATH,
+)
+client = importlib.util.module_from_spec(spec)
+spec.loader.exec_module(client)
+
+with tempfile.TemporaryDirectory() as directory:
+    socket_path = str(Path(directory) / "test.sock")
+    received = {}
+
+    listener = socket.socket(
+        socket.AF_UNIX,
+        socket.SOCK_STREAM,
+    )
+    listener.bind(socket_path)
+    listener.listen(1)
+
+    def serve():
+        connection, _ = listener.accept()
+
+        with connection:
+            raw = b""
+
+            while b"\n" not in raw:
+                chunk = connection.recv(65536)
+
+                if not chunk:
+                    break
+
+                raw += chunk
+
+            received.update(
+                json.loads(raw.decode().strip())
+            )
+
+            connection.sendall(
+                json.dumps({
+                    "protocol_version": 1,
+                    "ok": True,
+                    "resource": "postgresql-ha",
+                    "action": "notify",
+                    "result": {"ocf_rc": 0},
+                }).encode()
+                + b"\n"
+            )
+
+    thread = threading.Thread(target=serve)
+    thread.start()
+
+    client.send_request(
+        socket_path,
+        "postgresql-ha",
+        "notify",
+        {
+            "type": "pre",
+            "operation": "demote",
+        },
+    )
+
+    thread.join()
+    listener.close()
+
+    assert received["action"] == "notify"
+    assert received["parameters"] == {
+        "type": "pre",
+        "operation": "demote",
+    }
+
+print("PROXY_CLIENT_PARAMETER_TEST_PASS=1")