diff --git a/public/java/src/org/broadinstitute/sting/gatk/walkers/variantutils/SelectVariants.java b/public/java/src/org/broadinstitute/sting/gatk/walkers/variantutils/SelectVariants.java
index 98f56be1f..c7b1d0fc7 100755
--- a/public/java/src/org/broadinstitute/sting/gatk/walkers/variantutils/SelectVariants.java
+++ b/public/java/src/org/broadinstitute/sting/gatk/walkers/variantutils/SelectVariants.java
@@ -31,7 +31,6 @@ import org.broadinstitute.sting.gatk.arguments.StandardVariantContextInputArgume
 import org.broadinstitute.sting.gatk.contexts.AlignmentContext;
 import org.broadinstitute.sting.gatk.contexts.ReferenceContext;
 import org.broadinstitute.sting.gatk.refdata.RefMetaDataTracker;
-import org.broadinstitute.sting.gatk.walkers.NanoSchedulable;
 import org.broadinstitute.sting.gatk.walkers.RodWalker;
 import org.broadinstitute.sting.gatk.walkers.TreeReducible;
 import org.broadinstitute.sting.gatk.walkers.annotator.ChromosomeCounts;
@@ -189,7 +188,7 @@ import java.util.*;
  *
  */
 @DocumentedGATKFeature( groupName = "Variant Evaluation and Manipulation Tools", extraDocs = {CommandLineGATK.class} )
-public class SelectVariants extends RodWalker<Integer, Integer> implements TreeReducible<Integer>, NanoSchedulable {
+public class SelectVariants extends RodWalker<Integer, Integer> implements TreeReducible<Integer> {
     @ArgumentCollection protected StandardVariantContextInputArgumentCollection variantCollection = new StandardVariantContextInputArgumentCollection();
 
     /**
@@ -543,9 +542,11 @@ public class SelectVariants extends RodWalker<Integer, Integer> implements TreeR
             VariantContext sub = subsetRecord(vc, EXCLUDE_NON_VARIANTS);
 
             if ( REGENOTYPE && sub.isPolymorphicInSamples() && hasPLs(sub) ) {
-                final VariantContextBuilder builder = new VariantContextBuilder(UG_engine.calculateGenotypes(sub)).filters(sub.getFiltersMaybeNull());
-                addAnnotations(builder, sub);
-                sub = builder.make();
+                synchronized (UG_engine) {
+                    final VariantContextBuilder builder = new VariantContextBuilder(UG_engine.calculateGenotypes(sub)).filters(sub.getFiltersMaybeNull());
+                    addAnnotations(builder, sub);
+                    sub = builder.make();
+                }
             }
             
             if ( (!EXCLUDE_NON_VARIANTS || sub.isPolymorphicInSamples()) && (!EXCLUDE_FILTERED || !sub.isFiltered()) ) {