diff -r 0c1b091fb92b pypy/module/cpyext/test/test_bufferobject.py
--- a/pypy/module/cpyext/test/test_bufferobject.py	Sun Apr 08 12:03:19 2018 +0300
+++ b/pypy/module/cpyext/test/test_bufferobject.py	Sun Apr 08 11:07:48 2018 +0200
@@ -71,17 +71,15 @@
         module = self.import_extension('foo', [
             ("test_mod", 'METH_VARARGS',
             """
-                PyObject *obj, *collect, *tup;
+                PyObject *obj;
                 Py_buffer bp;
-                if (!PyArg_ParseTuple(args, "OO", &obj, &collect))
+                if (!PyArg_ParseTuple(args, "O", &obj))
                     return NULL;
 
                 assert(obj);
 
                 if (PyObject_GetBuffer(obj, &bp, PyBUF_SIMPLE) == -1)
                     return NULL;
-                
-                tup = PyTuple_New(0); /* for collect() */
                 if (((unsigned char*)bp.buf)[0] != '0') {
                     PyErr_Format(PyExc_ValueError,
                             "mismatch: 0x%x [%x %x %x %x...] instead of '0' (got len=%d)",
@@ -92,12 +90,10 @@
                             ((unsigned char*)bp.buf)[4],
                             bp.len);
                     PyBuffer_Release(&bp);
-                    Py_DECREF(tup);
                     return NULL;
                 }
 
                 PyBuffer_Release(&bp);
-                Py_DECREF(tup);
                 Py_RETURN_NONE;
             """),
             ])
@@ -114,7 +110,7 @@
             block = getdata(bufsize)
             assert block[:8] == '01234567'
             try:
-                module.test_mod(block, gc.collect)
+                module.test_mod(block)
             except ValueError as e:
                 print("%s at it=%d" % (e, j))
                 assert False