diff --git a/src/common/helpers.py b/src/common/helpers.py
index b37aad73eecaf386fe6d7e1862dfeb5a90a3e7cd..52f9ac0e3b7c28dd5be79357d93b343dbaaf4154 100644
--- a/src/common/helpers.py
+++ b/src/common/helpers.py
@@ -44,11 +44,7 @@
 class InvalidFormat(Exception):
 	pass
 
-def parse_jid(jidstring):
-	'''Perform stringprep on all JID fragments from a string
-	and return the full jid'''
-	# This function comes from http://svn.twistedmatrix.com/cvs/trunk/twisted/words/protocols/jabber/jid.py
-
+def decompose_jid(jidstring):
 	user = None
 	server = None
 	resource = None
@@ -80,8 +76,14 @@ def parse_jid(jidstring):
 				# server/resource (with an @ in resource)
 				server = jidstring[0:res_sep]
 				resource = jidstring[res_sep + 1:] or None
+	return user, server, resource
+
+def parse_jid(jidstring):
+	'''Perform stringprep on all JID fragments from a string
+	and return the full jid'''
+	# This function comes from http://svn.twistedmatrix.com/cvs/trunk/twisted/words/protocols/jabber/jid.py
 
-	return prep(user, server, resource)
+	return prep(*decompose_jid(jidstring))
 
 def parse_resource(resource):
 	'''Perform stringprep on resource and return it'''
diff --git a/src/dialogs.py b/src/dialogs.py
index e06111af393ba1814ad9502dcd386b017d6921d6..010ad98da2621d6adc4ee03469841247bccdb67e 100644
--- a/src/dialogs.py
+++ b/src/dialogs.py
@@ -1207,6 +1207,11 @@ def on_join_button_clicked(self, widget):
 		room_jid = self._room_jid_entry.get_text().decode('utf-8')
 		password = self.xml.get_widget('password_entry').get_text().decode(
 			'utf-8')
+		user, server, resource = helpers.decompose_jid(room_jid)
+		if not user or not server or resource:
+			ErrorDialog(_('Invalid group chat Jabber ID'),
+				_('The group chat Jabber ID has not allowed characters.'))
+			return
 		try:
 			room_jid = helpers.parse_jid(room_jid)
 		except: