diff --git a/src/config.test.ts b/src/config.test.ts
index ee0cadc..93927b2 100644
--- a/src/config.test.ts
+++ b/src/config.test.ts
@@ -1,7 +1,7 @@
 import assert from "node:assert/strict";
 import test from "node:test";
 
-import { loadConfig, parseDuration } from "./config.ts";
+import { loadConfig, parseDurationToMs } from "./config.ts";
 
 const baseEnv = {
   ATPROTO_HANDLE: "test.example",
@@ -50,10 +50,11 @@ test("invalid day and time throw", () => {
 });
 
 test("parseDuration handles Go-style durations", () => {
-  assert.equal(parseDuration("30s"), 30_000);
-  assert.equal(parseDuration("5m"), 300_000);
-  assert.equal(parseDuration("1h30m"), 5_400_000);
-  assert.throws(() => parseDuration("5"), /invalid duration/);
-  assert.throws(() => parseDuration("fast"), /invalid duration/);
-  assert.throws(() => parseDuration(""), /invalid duration/);
+  assert.equal(parseDurationToMs("30s"), 30_000);
+  assert.equal(parseDurationToMs("5m"), 300_000);
+  assert.equal(parseDurationToMs("1h30m"), 5_400_000);
+  assert.throws(() => parseDurationToMs("5"), /invalid duration/);
+  assert.throws(() => parseDurationToMs("fast"), /invalid duration/);
+  assert.throws(() => parseDurationToMs(""), /invalid duration/);
+  assert.throws(() => parseDurationToMs("249ms"), /must be at least 250ms/);
 });
diff --git a/src/config.ts b/src/config.ts
index 5483c3b..bbaff4d 100644
--- a/src/config.ts
+++ b/src/config.ts
@@ -50,7 +50,7 @@ export function loadConfig(env: Record<string, string | undefined> = process.env
     weeklyNotifyDay: dayIndex + 1,
     weeklyNotifyHour: hour,
     weeklyNotifyMinute: minute,
-    checkIntervalMs: parseDuration(required("CHECK_INTERVAL")),
+    checkIntervalMs: parseDurationToMs(required("CHECK_INTERVAL")),
     enableStdout: env.ENABLE_STDOUT === "true",
     openMeetBaseUrl: env.OPENMEET_BASE_URL || "https://api.openmeet.net",
     atprotoPdsUrl: env.ATPROTO_PDS_URL || undefined,
@@ -64,8 +64,7 @@ const DURATION_UNITS: Record<string, number> = {
   h: 3_600_000,
 };
 
-// Parses Go-style durations like "30s", "5m", "1h30m" into milliseconds.
-export function parseDuration(input: string): number {
+export function parseDurationToMs(input: string): number {
   let total = 0;
   let matched = "";
   for (const m of input.matchAll(/(\d+)(ms|s|m|h)/g)) {
@@ -75,5 +74,8 @@ export function parseDuration(input: string): number {
   if (matched !== input || input === "") {
     throw new Error(`invalid duration "${input}" (expected e.g. "30s", "5m", "1h")`);
   }
+  if (total < 250) {
+    throw new Error("check duration must be at least 250ms");
+  }
   return total;
 }