cap = uri.from_string(bigcap, deep_immutable=deep_immutable,
name=name)
node = self._create_from_single_cap(cap)
+
+ # node is None for an unknown URI, otherwise it is a type for which
+ # is_mutable() is known. We avoid cacheing mutable nodes due to
+ # ticket #1679.
if node is None:
# don't cache UnknownNode
node = UnknownNode(writecap, readcap,