diff --git a/ucs-school-umc-computerroom/umc/python/computerroom/__init__.py b/ucs-school-umc-computerroom/umc/python/computerroom/__init__.py
index 9da6be7..7945e3c 100644
--- a/ucs-school-umc-computerroom/umc/python/computerroom/__init__.py
+++ b/ucs-school-umc-computerroom/umc/python/computerroom/__init__.py
@@ -450,7 +450,7 @@ def update(self, request, ldap_user_read=None):
 		if not self._italc.school or not self._italc.room:
 			raise UMC_Error('no room selected')
 
-		computers = [computer.dict for computer in self._italc.values() if computer.hasChanged]
+		computers = self._italc.query()
 		result = {'computers': computers}
 
 		userDN = _getRoomOwner(self._italc.roomDN)
diff --git a/ucs-school-umc-computerroom/umc/python/computerroom/italc2.py b/ucs-school-umc-computerroom/umc/python/computerroom/italc2.py
index df7924f..c45e72d 100644
--- a/ucs-school-umc-computerroom/umc/python/computerroom/italc2.py
+++ b/ucs-school-umc-computerroom/umc/python/computerroom/italc2.py
@@ -183,7 +183,6 @@ def isInitialized(self):
 	def hasChanged(self):
 		self.lock()
 		diff = self._has_changed
-		self._has_changed = False
 		self._old = copy.deepcopy(self._current)
 		self.unlock()
 		return diff
@@ -390,6 +389,11 @@ def hasChanged(self):
 		states = (self.state, self.flags, self.user, self.teacher)
 		return any(state.hasChanged for state in states)
 
+	def reset_has_changed(self):
+		states = (self.state, self.flags, self.user, self.teacher)
+		for state in states:
+			state._has_changed = False
+
 	# UDM properties
 	@property
 	def name(self):
@@ -745,3 +749,10 @@ def stopDemo(self):
 			self.demoServer.stopDemoServer()
 		for client in self.demoClients:
 			client.stopDemoClient()
+
+	def query(self):
+		try:
+			return [computer.dict for computer in self._italc.values() if computer.hasChanged]
+		finally:
+			for computer in self._italc.values():
+				computer.reset_has_changed()