diff --git a/java/src/org/broadinstitute/sting/gatk/walkers/genotyper/GenotypeCalculationModel.java b/java/src/org/broadinstitute/sting/gatk/walkers/genotyper/GenotypeCalculationModel.java
index fa163dbd5..d1d25d4a9 100755
--- a/java/src/org/broadinstitute/sting/gatk/walkers/genotyper/GenotypeCalculationModel.java
+++ b/java/src/org/broadinstitute/sting/gatk/walkers/genotyper/GenotypeCalculationModel.java
@@ -1,6 +1,7 @@
 package org.broadinstitute.sting.gatk.walkers.genotyper;
 
 import org.broadinstitute.sting.gatk.contexts.AlignmentContext;
+import org.broadinstitute.sting.gatk.refdata.RefMetaDataTracker;
 import org.broadinstitute.sting.utils.genotype.GenotypeWriter;
 
 import java.util.*;
@@ -82,7 +83,8 @@ public abstract class GenotypeCalculationModel implements Cloneable {
      *
      * @return true if valid locus
      */
-    public abstract boolean calculateGenotype(char ref,
+    public abstract boolean calculateGenotype(RefMetaDataTracker tracker,
+                                              char ref,
                                               AlignmentContext context,
                                               DiploidGenotypePriors priors);
 }
\ No newline at end of file
diff --git a/java/src/org/broadinstitute/sting/gatk/walkers/genotyper/MultiSampleAllMAFsGenotypeCalculationModel.java b/java/src/org/broadinstitute/sting/gatk/walkers/genotyper/MultiSampleAllMAFsGenotypeCalculationModel.java
index 8423a734c..e94258462 100755
--- a/java/src/org/broadinstitute/sting/gatk/walkers/genotyper/MultiSampleAllMAFsGenotypeCalculationModel.java
+++ b/java/src/org/broadinstitute/sting/gatk/walkers/genotyper/MultiSampleAllMAFsGenotypeCalculationModel.java
@@ -2,6 +2,7 @@ package org.broadinstitute.sting.gatk.walkers.genotyper;
 
 import org.broadinstitute.sting.utils.genotype.GenotypeWriter;
 import org.broadinstitute.sting.gatk.contexts.AlignmentContext;
+import org.broadinstitute.sting.gatk.refdata.RefMetaDataTracker;
 
 import java.util.Set;
 
@@ -28,7 +29,7 @@ public class MultiSampleAllMAFsGenotypeCalculationModel extends GenotypeCalculat
         return super.clone();
     }
 
-    public boolean calculateGenotype(char ref, AlignmentContext context, DiploidGenotypePriors priors) {
+    public boolean calculateGenotype(RefMetaDataTracker tracker, char ref, AlignmentContext context, DiploidGenotypePriors priors) {
 
         // This is just a stub...
         // TODO --- implement me
diff --git a/java/src/org/broadinstitute/sting/gatk/walkers/genotyper/SingleSampleGenotypeCalculationModel.java b/java/src/org/broadinstitute/sting/gatk/walkers/genotyper/SingleSampleGenotypeCalculationModel.java
index db8b232ba..29b8f4ca5 100755
--- a/java/src/org/broadinstitute/sting/gatk/walkers/genotyper/SingleSampleGenotypeCalculationModel.java
+++ b/java/src/org/broadinstitute/sting/gatk/walkers/genotyper/SingleSampleGenotypeCalculationModel.java
@@ -1,6 +1,7 @@
 package org.broadinstitute.sting.gatk.walkers.genotyper;
 
 import org.broadinstitute.sting.gatk.contexts.AlignmentContext;
+import org.broadinstitute.sting.gatk.refdata.RefMetaDataTracker;
 import org.broadinstitute.sting.utils.*;
 import org.broadinstitute.sting.utils.genotype.GenotypeWriter;
 
@@ -37,7 +38,7 @@ public class SingleSampleGenotypeCalculationModel extends GenotypeCalculationMod
         return super.clone();
     }
 
-    public boolean calculateGenotype(char ref, AlignmentContext context, DiploidGenotypePriors priors) {
+    public boolean calculateGenotype(RefMetaDataTracker tracker, char ref, AlignmentContext context, DiploidGenotypePriors priors) {
 
         GenotypeLikelihoods gl = GenotypeLikelihoodsFactory.makeGenotypeLikelihoods(baseModel, priors, defaultPlatform);
         gl.setVerbose(VERBOSE);
diff --git a/java/src/org/broadinstitute/sting/gatk/walkers/genotyper/UnifiedGenotyper.java b/java/src/org/broadinstitute/sting/gatk/walkers/genotyper/UnifiedGenotyper.java
index 99fa0a6f8..62b64d9e4 100755
--- a/java/src/org/broadinstitute/sting/gatk/walkers/genotyper/UnifiedGenotyper.java
+++ b/java/src/org/broadinstitute/sting/gatk/walkers/genotyper/UnifiedGenotyper.java
@@ -90,7 +90,7 @@ public class UnifiedGenotyper extends LocusWalker<Integer, Integer> {
             return 0;
 
         DiploidGenotypePriors priors = new DiploidGenotypePriors(ref, UAC.heterozygosity, DiploidGenotypePriors.PROB_OF_TRISTATE_GENOTYPE);
-        return ( gcm.calculateGenotype(ref, context, priors) ?  1 : 0 );
+        return ( gcm.calculateGenotype(tracker, ref, context, priors) ?  1 : 0 );
     }
 
     /**