diff --git a/tools/rgenetics/rgClustalw.xml b/tools/rgenetics/rgClustalw.xml
index e31045703ef..cc8eb2cf495 100644
--- a/tools/rgenetics/rgClustalw.xml
+++ b/tools/rgenetics/rgClustalw.xml
@@ -1,4 +1,5 @@
 <tool id="clustalw" name="ClustalW" version="0.1">
+   <requirements><requirement type="package">clustalw2</requirement></requirements>
    <description>multiple sequence alignment program for DNA or proteins</description>
    <command interpreter="python"> 
     rgClustalw.py -i "$input" -o "$output" -s "$out_order" -l "$outlog" -t "$outname" -d "$dnarna"