diff --git a/docs/18170_run_notes.md b/docs/18170_run_notes.md
index 46f9fec4eb79e620062c16408fe97beae708a497..7a02927f982a98e3c5c39a9da9e4d1e92eed3ac6 100644
--- a/docs/18170_run_notes.md
+++ b/docs/18170_run_notes.md
@@ -74,7 +74,7 @@ done
 Re-generate the family ids list.
 
 ```
-cut -f 1 /scratch/u035/project/trio_whole_exome/analysis/params/18170_Ansari_Morad.ped > 18170_Ansari_Morad.family_ids.txt
+cut -f 1 /scratch/u035/project/trio_whole_exome/analysis/params/18170_Ansari_Morad.ped | sort -u > 18170_Ansari_Morad.family_ids.txt
 ```
 
 Edit the parameter generation script to skip running the Perl script for producing the PED files.