BytesIO.getvalue() and StringIO.getvalue() are METH_NOARGS.
diff --git a/Modules/_io/stringio.c b/Modules/_io/stringio.c
index 13e3b58..5bb80cb 100644
--- a/Modules/_io/stringio.c
+++ b/Modules/_io/stringio.c
@@ -827,7 +827,7 @@
 
 static struct PyMethodDef stringio_methods[] = {
     {"close",    (PyCFunction)stringio_close,    METH_NOARGS,  stringio_close_doc},
-    {"getvalue", (PyCFunction)stringio_getvalue, METH_VARARGS, stringio_getvalue_doc},
+    {"getvalue", (PyCFunction)stringio_getvalue, METH_NOARGS,  stringio_getvalue_doc},
     {"read",     (PyCFunction)stringio_read,     METH_VARARGS, stringio_read_doc},
     {"readline", (PyCFunction)stringio_readline, METH_VARARGS, stringio_readline_doc},
     {"tell",     (PyCFunction)stringio_tell,     METH_NOARGS,  stringio_tell_doc},