diff --git a/ChangeLog b/ChangeLog
index 9c9b3b4a..0e721f3f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2010-11-17  Daniele Varrazzo  <daniele.varrazzo@gmail.com>
+
+	* psycopg/connection_type.c: don't clobber exception if
+	isolation_level_switch fails.
+
 2010-11-16  Daniele Varrazzo  <daniele.varrazzo@gmail.com>
 
 	* psycopg/connection_int.c: abort connection to protocol 2 server.
diff --git a/psycopg/connection_type.c b/psycopg/connection_type.c
index dce2f40d..f6781090 100644
--- a/psycopg/connection_type.c
+++ b/psycopg/connection_type.c
@@ -415,12 +415,9 @@ psyco_conn_set_isolation_level(connectionObject *self, PyObject *args)
     }
 
     if (conn_switch_isolation_level(self, level) < 0) {
-        PyErr_SetString(OperationalError,
-                        PQerrorMessage(self->pgconn));
         return NULL;
     }
 
-
     Py_INCREF(Py_None);
     return Py_None;
 }