diff --git a/relational/relation.py b/relational/relation.py
index f69733c..b42169b 100644
--- a/relational/relation.py
+++ b/relational/relation.py
@@ -54,7 +54,6 @@ class Relation (object):
 
     def __init__(self, filename=""):
         self._readonly = False
-        self._copy = None
         self.content = set()
 
         if len(filename) == 0:  # Empty relation
@@ -71,8 +70,6 @@ class Relation (object):
 
         self._readonly = True
         copy._readonly = True
-        copy._copy = self
-        self._copy = copy
 
     def _make_writable(self, copy_content=True):
         '''If this relation is marked as readonly, this
@@ -83,8 +80,6 @@ class Relation (object):
 
         if self._readonly:
             self._readonly = False
-            self._copy._readonly = False
-            self._copy = None
 
             if copy_content:
                 self.content = set(self.content)
diff --git a/test/update.py b/test/update.py
new file mode 100644
index 0000000..b0d0b6a
--- /dev/null
+++ b/test/update.py
@@ -0,0 +1,16 @@
+p1=people
+p2=p1.rename({'id':'i'})
+p2=p2.rename({'i':'id'})
+assert p1==p2
+assert p1._readonly
+assert p2._readonly
+# It is VERY important to not change the original relations
+# or other tests might fail randomly, since the relations are
+# only loaded once
+
+p2.update('age==20', {'age':50})
+assert p2._readonly == False
+assert p1!=p2
+p3 = p2.selection('age!=50')
+p4 = p1.selection('age!=20')
+assert p3==p4