diff --git a/clen_tools/sample_crystfel-ls.py b/clen_tools/sample_crystfel-ls.py
index 5878653..eb91a01 100644
--- a/clen_tools/sample_crystfel-ls.py
+++ b/clen_tools/sample_crystfel-ls.py
@@ -45,7 +45,7 @@ def h5_sample( lst, sample ):
 
     # write sample to file
     print( "writing to file" )
-    sample_file = "{0}_{1}".format( sample, lst_name )
+    sample_file = "{0}_{1}.lst".format( sample, lst_name )
     sample_df.to_csv( sample_file, sep=" ", index=False, header=False )
     print( "done" )