diff --git a/scripts/merge_skymodels.py b/scripts/merge_skymodels.py
index 1a5a8728f2b6397ed788e9624f3b6eb3874591d0..ba27002312ed595a977c7d6619f1e2323d86cd72 100644
--- a/scripts/merge_skymodels.py
+++ b/scripts/merge_skymodels.py
@@ -5,6 +5,7 @@ Append a LOFAR skymodel to an existing one
 
 import os, logging
 import lsmtool
+import numpy
 
 ########################################################################
 
@@ -15,8 +16,13 @@ def main(inmodel1, inmodel2, outmodel = 'output.skymodel'):
     logging.info('Reading ' + inmodel2)
     s2 = lsmtool.load(inmodel2)
 
+    if s1.getPatchNames() is None:
+        s1.group('single')
+    if s2.getPatchNames() is None:
+        s2.group('single')
+
     logging.info('Adding skymodel ' + inmodel2 + ' to ' + inmodel1)
-    s1.concatenate(s2)
+    s1.concatenate(s2, inheritPatches=True)
     s1.write(outmodel)
 
     return(0)