Index: Python/errors.c
===================================================================
--- Python/errors.c	(révision 65930)
+++ Python/errors.c	(copie de travail)
@@ -66,6 +66,8 @@
 	if (tstate->exc_value != NULL && tstate->exc_value != Py_None) {
 		/* Implicit exception chaining */
 		if (value == NULL || !PyExceptionInstance_Check(value)) {
+			PyObject *exc_value_copy;
+
 			/* We must normalize the value right now */
 			PyObject *args, *fixed_value;
 			if (value == NULL || value == Py_None)
@@ -76,8 +78,19 @@
 			}
 			else
 				args = PyTuple_Pack(1, value);
+
+			exc_value_copy = tstate->exc_value;
+			Py_INCREF(exc_value_copy);
+
 			fixed_value = args ?
 				PyEval_CallObject(exception, args) : NULL;
+
+			Py_DECREF(exc_value_copy);
+			if (tstate->exc_value != exc_value_copy) {
+				Py_XDECREF(tstate->exc_value);
+				tstate->exc_value = exc_value_copy;
+			}
+
 			Py_XDECREF(args);
 			Py_XDECREF(value);
 			if (fixed_value == NULL)