diff --git a/CEP/Pipeline/recipes/sip/nodes/imager_prepare.py b/CEP/Pipeline/recipes/sip/nodes/imager_prepare.py
index cf92cfec036ae5d59c63fac6be9ce94e44ad0ba6..a33129845e4d780df1b08f9b37697e145c805611 100644
--- a/CEP/Pipeline/recipes/sip/nodes/imager_prepare.py
+++ b/CEP/Pipeline/recipes/sip/nodes/imager_prepare.py
@@ -124,7 +124,7 @@ class imager_prepare(LOFARnodeTCP):
 
         return 0
 
-    def add_beam_tables(time_slices_path_list):
+    def add_beam_tables(self, time_slices_path_list):
         beamtable_proc_group = SubProcessGroup(self.logger)
         for ms_path in time_slices_path_list:
             cmd_string = "makebeamtables ms={0} overwrite=true".format(ms_path)