diff --git a/src/netsleuth/cli.py b/src/netsleuth/cli.py
index 77ef25c..327d63c 100644
--- a/src/netsleuth/cli.py
+++ b/src/netsleuth/cli.py
@@ -516,6 +516,7 @@ async def _speed_section(client, settings: Settings, options: Options, idle_rtt_
     import shutil
 
     from netsleuth.speed import (
+        BufferbloatMeasureConfig,
         measure_with_bufferbloat,
         run_speed_cascade,
         tier_cloudflare,
@@ -559,12 +560,14 @@ async def _speed_section(client, settings: Settings, options: Options, idle_rtt_
 
     result = await measure_with_bufferbloat(
         result,
-        idle_rtt_ms=idle_rtt_ms if result.idle_rtt_ms is None else result.idle_rtt_ms,
-        bands=settings.thresholds.bufferbloat_ms,
-        run_download=_saturate_down,
-        run_upload=_saturate_up,
-        probe=_probe,
-        interval=cfg.bufferbloat_probe_interval_seconds,
+        config=BufferbloatMeasureConfig(
+            idle_rtt_ms=idle_rtt_ms if result.idle_rtt_ms is None else result.idle_rtt_ms,
+            bands=settings.thresholds.bufferbloat_ms,
+            run_download=_saturate_down,
+            run_upload=_saturate_up,
+            probe=_probe,
+            interval=cfg.bufferbloat_probe_interval_seconds,
+        ),
     )
     return ModuleResult(name="speed", status="ok", data=result)
 
diff --git a/src/netsleuth/speed.py b/src/netsleuth/speed.py
index 505e1f0..0b1cbfe 100644
--- a/src/netsleuth/speed.py
+++ b/src/netsleuth/speed.py
@@ -61,6 +61,7 @@ def bufferbloat_delta(idle_rtt_ms: float | None, loaded_rtts_ms: list[float]) ->
 import asyncio
 import time
 from collections.abc import Awaitable, Callable
+from dataclasses import dataclass
 
 from netsleuth.models import SpeedResult, TierAttempt
 
@@ -241,6 +242,16 @@ from netsleuth.interpret import grade_bufferbloat
 from netsleuth.stats import rtt_stats
 
 
+@dataclass(frozen=True)
+class BufferbloatMeasureConfig:
+    idle_rtt_ms: float | None
+    bands: BufferbloatBands
+    run_download: Callable[[], Awaitable[None]]
+    run_upload: Callable[[], Awaitable[None]]
+    probe: Callable[[], Awaitable[float | None]]
+    interval: float
+
+
 async def probe_while(
     coro: Awaitable[None],
     probe: Callable[[], Awaitable[float | None]],
@@ -259,25 +270,20 @@ async def probe_while(
 
 async def measure_with_bufferbloat(
     result: SpeedResult,
-    idle_rtt_ms: float | None,
-    bands: BufferbloatBands,
-    run_download: Callable[[], Awaitable[None]],
-    run_upload: Callable[[], Awaitable[None]],
-    probe: Callable[[], Awaitable[float | None]],
-    interval: float,
+    config: BufferbloatMeasureConfig,
 ) -> SpeedResult:
     # This is the one place a measurement is allowed to overlap another: the
     # whole point is to see what latency does while the link is saturated.
-    down_samples = await probe_while(run_download(), probe, interval)
-    up_samples = await probe_while(run_upload(), probe, interval)
-    result.idle_rtt_ms = idle_rtt_ms
+    down_samples = await probe_while(config.run_download(), config.probe, config.interval)
+    up_samples = await probe_while(config.run_upload(), config.probe, config.interval)
+    result.idle_rtt_ms = config.idle_rtt_ms
     result.loaded_rtt_down_ms = rtt_stats(list(down_samples)).avg_ms
     result.loaded_rtt_up_ms = rtt_stats(list(up_samples)).avg_ms
-    result.bufferbloat_down_ms = bufferbloat_delta(idle_rtt_ms, down_samples)
-    result.bufferbloat_up_ms = bufferbloat_delta(idle_rtt_ms, up_samples)
+    result.bufferbloat_down_ms = bufferbloat_delta(config.idle_rtt_ms, down_samples)
+    result.bufferbloat_up_ms = bufferbloat_delta(config.idle_rtt_ms, up_samples)
     worst_delta = max(
         [d for d in (result.bufferbloat_down_ms, result.bufferbloat_up_ms) if d is not None],
         default=None,
     )
-    result.bufferbloat_grade = grade_bufferbloat(worst_delta, bands)
+    result.bufferbloat_grade = grade_bufferbloat(worst_delta, config.bands)
     return result
diff --git a/tests/test_speed.py b/tests/test_speed.py
index 3722359..019bafd 100644
--- a/tests/test_speed.py
+++ b/tests/test_speed.py
@@ -14,7 +14,7 @@ from netsleuth.models import SpeedResult
 from netsleuth.speed import NDT7_CONSENT_NOTICE, run_speed_cascade
 from netsleuth.speed import tier_ookla
 from netsleuth.config import BufferbloatBands
-from netsleuth.speed import measure_with_bufferbloat, probe_while
+from netsleuth.speed import BufferbloatMeasureConfig, measure_with_bufferbloat, probe_while
 import httpx
 from pytest_httpx import HTTPXMock
 from netsleuth.config import Speedtest
@@ -371,12 +371,14 @@ async def test_measure_with_bufferbloat_fills_in_both_directions_and_the_grade()
 
     result = await measure_with_bufferbloat(
         SpeedResult(method="cloudflare", download_mbps=300.0, upload_mbps=40.0),
-        idle_rtt_ms=12.0,
-        bands=BufferbloatBands(),
-        run_download=run_download,
-        run_upload=run_upload,
-        probe=probe,
-        interval=0.05,
+        config=BufferbloatMeasureConfig(
+            idle_rtt_ms=12.0,
+            bands=BufferbloatBands(),
+            run_download=run_download,
+            run_upload=run_upload,
+            probe=probe,
+            interval=0.05,
+        ),
     )
     assert result.idle_rtt_ms == 12.0
     assert result.loaded_rtt_down_ms is not None
@@ -396,12 +398,14 @@ async def test_measure_with_bufferbloat_without_an_idle_baseline_grades_unknown(
 
     result = await measure_with_bufferbloat(
         SpeedResult(method="cloudflare", download_mbps=300.0),
-        idle_rtt_ms=None,
-        bands=BufferbloatBands(),
-        run_download=work,
-        run_upload=work,
-        probe=probe,
-        interval=0.02,
+        config=BufferbloatMeasureConfig(
+            idle_rtt_ms=None,
+            bands=BufferbloatBands(),
+            run_download=work,
+            run_upload=work,
+            probe=probe,
+            interval=0.02,
+        ),
     )
     assert result.bufferbloat_down_ms is None
     assert result.bufferbloat_grade == "?"