diff --git a/Lib/test/pickletester.py b/Lib/test/pickletester.py
index 6ef4c8989f5..7758ff8ef9e 100644
--- a/Lib/test/pickletester.py
+++ b/Lib/test/pickletester.py
@@ -3404,7 +3404,10 @@ class AbstractPicklerUnpicklerObjectTests(unittest.TestCase):
     def test_multiple_unpicklings_minimal(self):
         # File-like object that doesn't support peek() and readinto()
         # (bpo-39681)
-        self._check_multiple_unpicklings(MinimalIO, seekable=False)
+        import warnings
+        with warnings.catch_warnings():
+            warnings.simplefilter("ignore", DeprecationWarning)
+            self._check_multiple_unpicklings(MinimalIO, seekable=False)
 
     def test_unpickling_buffering_readline(self):
         # Issue #12687: the unpickler's buffering logic could fail with
diff --git a/Modules/_pickle.c b/Modules/_pickle.c
index c3385ad3b9e..2b9d3f6f73d 100644
--- a/Modules/_pickle.c
+++ b/Modules/_pickle.c
@@ -1384,6 +1384,11 @@ _Unpickler_ReadInto(UnpicklerObject *self, char *buf, Py_ssize_t n)
     if (!self->readinto) {
         /* readinto() not supported on file-like object, fall back to read()
          * and copy into destination buffer (bpo-39681) */
+        if (PyErr_WarnEx(PyExc_DeprecationWarning,
+                         "file-like object should provide readinto()",
+                         1) < 0) {
+            return -1;
+        }
         PyObject* len = PyLong_FromSsize_t(n);
         if (len == NULL) {
             return -1;