diff --git a/README.md b/README.md
index f6ecb9d..c67c1bd 100644
--- a/README.md
+++ b/README.md
@@ -343,7 +343,7 @@ internally.
     the test is `TODO`. **Default:** `false`.
   - `timeout` {number} A number of milliseconds the test will fail after.
     If unspecified, subtests inherit this value from their parent.
-    **Default:** `30_000`.
+    **Default:** `Infinity`.
 - `fn` {Function|AsyncFunction} The function under test. The first argument
   to this function is a [`TestContext`][] object. If the test uses callbacks,
   the callback function is passed as the second argument. **Default:** A no-op
@@ -376,6 +376,11 @@ test('top level test', async t => {
 })
 ```
 
+The `timeout` option can be used to fail the test if it takes longer than
+`timeout` milliseconds to complete. However, it is not a reliable mechanism for
+canceling tests because a running test might block the application thread and
+thus prevent the scheduled cancellation.
+
 ## `describe([name][, options][, fn])`
 
 * `name` {string} The name of the suite, which is displayed when reporting test
@@ -501,7 +506,7 @@ execution of the test function. This function does not return a value.
     the test is `TODO`. **Default:** `false`.
   - `timeout` {number} A number of milliseconds the test will fail after.
     If unspecified, subtests inherit this value from their parent.
-    **Default:** `30_000`.
+    **Default:** `Infinity`.
 - `fn` {Function|AsyncFunction} The function under test. The first argument
   to this function is a [`TestContext`][] object. If the test uses callbacks,
   the callback function is passed as the second argument. **Default:** A no-op