diff --git a/sameas/templatetags/sameastags.py b/sameas/templatetags/sameastags.py
index ba44760..dcd3dd5 100644
--- a/sameas/templatetags/sameastags.py
+++ b/sameas/templatetags/sameastags.py
@@ -62,7 +62,8 @@ def __init__(self, name, nodelist, parent=None):
 
     def render(self, context):
         result = super(BlockNodeProxy, self).render(context)
-        context.setdefault(_block_key(self.name), self)
+        if _block_key(self.name) not in context:
+            context[_block_key(self.name)] = self
         return result