diff --git a/python/src/ipaaca.py b/python/src/ipaaca.py
index 7055bddce657aeef593a75b796c8bf766d721959..f4fcfacb6bcc93ab608b304b20df7d06ba5a1bf7 100755
--- a/python/src/ipaaca.py
+++ b/python/src/ipaaca.py
@@ -1038,7 +1038,9 @@ class OutputBuffer(Buffer):
 		#if iu._uid is not None:
 		#	raise IUPublishedError(iu)
 		#iu.uid = self._generate_iu_uid()
-		self._iu_store[iu._uid] = iu
+	 	if iu.uid in self._iu_store:
+			raise IUPublishedError(iu)
+		self._iu_store[iu.uid] = iu
 		iu.buffer = self
 		self._publish_iu(iu)