diff --git a/tests/plugins/host_agent/test_agent_docker.py b/tests/plugins/host_agent/test_agent_docker.py
index 6bbe07d..dbf7044 100644
--- a/tests/plugins/host_agent/test_agent_docker.py
+++ b/tests/plugins/host_agent/test_agent_docker.py
@@ -569,7 +569,7 @@ def test_collect_docker_logs_since_cursor_and_dedup(monkeypatch):
 
     def fake_raw(socket_path, path, timeout=a.DOCKER_API_TIMEOUT):
         calls.append(path)
-        if "tail=" in path:            # first interval seeds from a tail
+        if "since=" not in path:       # first interval seeds from a tail alone
             return _frame(1, f"{t1} a\n".encode()) + _frame(1, f"{t2} b\n".encode())
         # second interval: daemon re-returns the boundary line (t2) + a new one
         return _frame(1, f"{t2} b\n".encode()) + _frame(1, f"{t3} c\n".encode())
@@ -584,6 +584,7 @@ def test_collect_docker_logs_since_cursor_and_dedup(monkeypatch):
     # boundary line b (t2) deduped against the cursor; only c (t3) is new
     assert [r["line"] for r in second] == ["c"]
     assert "since=" in calls[1]
+    assert f"tail={a.DOCKER_LOG_MAX_LINES}" in calls[1]   # bounded even since the cursor (#5764)
 
 
 def test_collect_docker_logs_excludes_and_skips_non_running(monkeypatch):