Index: Objects/setobject.c
===================================================================
--- Objects/setobject.c	(revision 80156)
+++ Objects/setobject.c	(working copy)
@@ -96,10 +96,13 @@
 			startkey = entry->key;
 			Py_INCREF(startkey);
 			cmp = PyObject_RichCompareBool(startkey, key, Py_EQ);
-			Py_DECREF(startkey);
-			if (cmp < 0)
+			if (cmp < 0) {
+				Py_DECREF(startkey);
 				return NULL;
-			if (table == so->table && entry->key == startkey) {
+			}
+			if (table == so->table && entry->key == startkey && Py_REFCNT(startkey) >= 2) {
+				/* since refcnt >= 2, this decref cannot trigger any weirdness */
+				Py_DECREF(startkey);   
 				if (cmp > 0)
 					return entry;
 			}
@@ -107,6 +110,7 @@
 				/* The compare did major nasty stuff to the
 				 * set:  start over.
  				 */
+				Py_DECREF(startkey);
  				return set_lookkey(so, key, hash);
  			}
 		}
@@ -129,17 +133,21 @@
 			startkey = entry->key;
 			Py_INCREF(startkey);
 			cmp = PyObject_RichCompareBool(startkey, key, Py_EQ);
-			Py_DECREF(startkey);
-			if (cmp < 0)
+			if (cmp < 0) {
+				Py_DECREF(startkey);
 				return NULL;
-			if (table == so->table && entry->key == startkey) {
-				if (cmp > 0)
+			}
+			if (table == so->table && entry->key == startkey && Py_REFCNT(startkey) >= 2) {
+				if (cmp > 0) {
+					Py_DECREF(startkey);
 					break;
+				}
 			}
 			else {
 				/* The compare did major nasty stuff to the
 				 * set:  start over.
  				 */
+				Py_DECREF(startkey);
  				return set_lookkey(so, key, hash);
  			}
 		}