diff --git a/Lib/test/test_optparse.py b/Lib/test/test_optparse.py
index 3c8c6124a25..7621c243055 100644
--- a/Lib/test/test_optparse.py
+++ b/Lib/test/test_optparse.py
@@ -395,6 +395,7 @@ def test_remove_nonexistent(self):
         self.assertRaises(self.parser.remove_option, ('foo',), None,
                           ValueError, "no such option 'foo'")
 
+    @support.impl_detail('Relies on sys.getrefcount', cpython=True)
     def test_refleak(self):
         # If an OptionParser is carrying around a reference to a large
         # object, various cycles can prevent it from being GC'd in
diff --git a/Modules/_io/iobase.c b/Modules/_io/iobase.c
index e3729902d88..ef06b43ca6e 100644
--- a/Modules/_io/iobase.c
+++ b/Modules/_io/iobase.c
@@ -42,8 +42,8 @@ PyDoc_STRVAR(iobase_doc,
     "bytes. bytearrays are accepted too, and in some cases (such as\n"
     "readinto) needed. Text I/O classes work with str data.\n"
     "\n"
-    "Note that calling any method (even inquiries) on a closed stream is\n"
-    "undefined. Implementations may raise IOError in this case.\n"
+    "Note that calling any method (except additional calls to close(),\n"
+    "which are ignored) on a closed stream should raise a ValueError.\n"
     "\n"
     "IOBase (and its subclasses) support the iterator protocol, meaning\n"
     "that an IOBase object can be iterated over yielding the lines in a\n"