Update graph operator overloading for subclasses

1 files changed, 3 insertions, 3 deletions

diff --git a/rdflib/graph.py b/rdflib/graph.py
index f90b3acb..c354a770 100644
--- a/rdflib/graph.py
+++ b/rdflib/graph.py
@@ -558,7 +558,7 @@ class Graph(Node):
     def __add__(self, other):
         """Set-theoretic union
            BNode IDs are not changed."""
-        retval = Graph()
+        retval = self.__class__()
         for (prefix, uri) in set(list(self.namespaces()) + list(other.namespaces())):
             retval.bind(prefix, uri)
         for x in self:
@@ -570,7 +570,7 @@ class Graph(Node):
     def __mul__(self, other):
         """Set-theoretic intersection.
            BNode IDs are not changed."""
-        retval = Graph()
+        retval = self.__class__()
         for x in other:
             if x in self:
                 retval.add(x)
@@ -579,7 +579,7 @@ class Graph(Node):
     def __sub__(self, other):
         """Set-theoretic difference.
            BNode IDs are not changed."""
-        retval = Graph()
+        retval = self.__class__()
         for x in self:
             if x not in other:
                 retval.add(x)