diff --git a/java/src/org/broadinstitute/sting/gatk/GATKArgumentCollection.java b/java/src/org/broadinstitute/sting/gatk/GATKArgumentCollection.java
index b2dbb7edd..0c0a96606 100755
--- a/java/src/org/broadinstitute/sting/gatk/GATKArgumentCollection.java
+++ b/java/src/org/broadinstitute/sting/gatk/GATKArgumentCollection.java
@@ -57,7 +57,7 @@ public class GATKArgumentCollection {
     public Map<String, String> walkerArgs = new HashMap<String, String>();    
 
     // parameters and their defaults
-    @ElementList
+    @ElementList(required=false)
     @Argument(fullName = "input_file", shortName = "I", doc = "SAM or BAM file(s)", required = false)
     public List<File> samFiles = new ArrayList<File>();