diff --git a/NEWS b/NEWS
index ca91abef..1ca96e6d 100644
--- a/NEWS
+++ b/NEWS
@@ -1,3 +1,10 @@
+What's new in psycopg 2.4.5
+---------------------------
+
+  - Fixed fetchmany() with no argument in cursor subclasses
+    (ticket #84).
+
+
 What's new in psycopg 2.4.4
 ---------------------------
 
diff --git a/psycopg/cursor_type.c b/psycopg/cursor_type.c
index 357b1a0b..bb9db691 100644
--- a/psycopg/cursor_type.c
+++ b/psycopg/cursor_type.c
@@ -850,13 +850,23 @@ psyco_curs_fetchmany(cursorObject *self, PyObject *args, PyObject *kwords)
     int i;
     PyObject *list, *res;
 
+    PyObject *pysize = NULL;
     long int size = self->arraysize;
     static char *kwlist[] = {"size", NULL};
 
-    if (!PyArg_ParseTupleAndKeywords(args, kwords, "|l", kwlist, &size)) {
+    /* allow passing None instead of omitting the *size* argument,
+     * or using the method from subclasses would be a problem */
+    if (!PyArg_ParseTupleAndKeywords(args, kwords, "|O", kwlist, &pysize)) {
         return NULL;
     }
 
+    if (pysize && pysize != Py_None) {
+        size = PyInt_AsLong(pysize);
+        if (size == -1 && PyErr_Occurred()) {
+            return NULL;
+        }
+    }
+
     EXC_IF_CURS_CLOSED(self);
     if (_psyco_curs_prefetch(self) < 0) return NULL;
     EXC_IF_NO_TUPLES(self);