diff --git a/java/src/org/broadinstitute/sting/playground/gatk/walkers/FlagStatReadWalker.java b/java/src/org/broadinstitute/sting/playground/gatk/walkers/FlagStatReadWalker.java
index 03fe72bbc..f487f8ab8 100644
--- a/java/src/org/broadinstitute/sting/playground/gatk/walkers/FlagStatReadWalker.java
+++ b/java/src/org/broadinstitute/sting/playground/gatk/walkers/FlagStatReadWalker.java
@@ -6,6 +6,8 @@ import java.text.DecimalFormat;
 import java.text.NumberFormat;
 
 import org.broadinstitute.sting.gatk.walkers.ReadWalker;
+import org.broadinstitute.sting.gatk.walkers.Requires;
+import org.broadinstitute.sting.gatk.walkers.DataSource;
 
 
 /*
@@ -41,9 +43,8 @@ import org.broadinstitute.sting.gatk.walkers.ReadWalker;
  *         This walker mirrors that stats that are generated by the flagstat
  *         command of samtools.
  */
+@Requires({DataSource.READS})
 public class FlagStatReadWalker extends ReadWalker<Integer, Integer> {
-
-
     // what comes out of the flagstat
     class FlagStat {
         int readCount = 0;