diff --git a/public/java/src/org/broadinstitute/sting/gatk/traversals/TraverseReadsNano.java b/public/java/src/org/broadinstitute/sting/gatk/traversals/TraverseReadsNano.java
index ee71d82bb..aa33def62 100755
--- a/public/java/src/org/broadinstitute/sting/gatk/traversals/TraverseReadsNano.java
+++ b/public/java/src/org/broadinstitute/sting/gatk/traversals/TraverseReadsNano.java
@@ -65,7 +65,8 @@ public class TraverseReadsNano<M,T> extends TraversalEngine<M,T,ReadWalker<M,T>,
             @Override
             public void progress(MapData lastProcessedMap) {
                 if ( lastProcessedMap.refContext != null )
-                    printProgress(lastProcessedMap.refContext.getLocus());
+                    // note, need to use getStopLocation so we don't give an interval to ProgressMeterDaemon
+                    printProgress(lastProcessedMap.refContext.getLocus().getStopLocation());
             }
         });
     }
diff --git a/public/java/src/org/broadinstitute/sting/utils/progressmeter/ProgressMeter.java b/public/java/src/org/broadinstitute/sting/utils/progressmeter/ProgressMeter.java
index c9d849227..b36326722 100755
--- a/public/java/src/org/broadinstitute/sting/utils/progressmeter/ProgressMeter.java
+++ b/public/java/src/org/broadinstitute/sting/utils/progressmeter/ProgressMeter.java
@@ -234,11 +234,13 @@ public class ProgressMeter {
      * the progress itself.  A separate printing daemon periodically polls the meter to print out
      * progress
      *
-     * @param loc       Current location, can be null if you are at the end of the processing unit
+     * @param loc Current location, can be null if you are at the end of the processing unit.  Must
+     *            have size == 1 (cannot be multiple bases in size).
      * @param nTotalRecordsProcessed the total number of records we've processed
      */
     public synchronized void notifyOfProgress(final GenomeLoc loc, final long nTotalRecordsProcessed) {
         if ( nTotalRecordsProcessed < 0 ) throw new IllegalArgumentException("nTotalRecordsProcessed must be >= 0");
+        if ( loc.size() != 1 ) throw new IllegalArgumentException("GenomeLoc must have size == 1 but got " + loc);
 
         // weird comparison to ensure that loc == null (in unmapped reads) is keep before maxGenomeLoc == null (on startup)
         this.maxGenomeLoc = loc == null ? loc : (maxGenomeLoc == null ? loc : loc.max(maxGenomeLoc));