diff --git a/tests/test_error.py b/tests/test_error.py
index 72446267..6e736330 100644
--- a/tests/test_error.py
+++ b/tests/test_error.py
@@ -2,6 +2,7 @@
 # SPDX-FileCopyrightText: 2021 Taneli Hukkinen
 # Licensed to PSF under a Contributor Agreement.
 
+import io
 import unittest
 
 from . import tomllib
@@ -55,3 +56,11 @@ def list_returner(s: str) -> list:
             self.assertEqual(
                 str(exc_info.exception), "parse_float must not return dicts or lists"
             )
+
+    def test_text_mode_error(self):
+        with self.assertRaises(TypeError) as exc_info:
+            tomllib.load(io.StringIO())  # type: ignore[arg-type]
+        self.assertEqual(
+            str(exc_info.exception),
+            "File must be opened in binary mode, e.g. use `open('foo.toml', 'rb')`",
+        )