diff --git a/protected/gatk-tools-protected/src/main/java/org/broadinstitute/gatk/tools/walkers/haplotypecaller/HaplotypeCallerGenotypingEngine.java b/protected/gatk-tools-protected/src/main/java/org/broadinstitute/gatk/tools/walkers/haplotypecaller/HaplotypeCallerGenotypingEngine.java
index f3b7e68ec..7f19861bc 100644
--- a/protected/gatk-tools-protected/src/main/java/org/broadinstitute/gatk/tools/walkers/haplotypecaller/HaplotypeCallerGenotypingEngine.java
+++ b/protected/gatk-tools-protected/src/main/java/org/broadinstitute/gatk/tools/walkers/haplotypecaller/HaplotypeCallerGenotypingEngine.java
@@ -73,6 +73,8 @@ public class HaplotypeCallerGenotypingEngine extends GenotypingEngine<HaplotypeC
 
     private final static List<Allele> NO_CALL = Collections.singletonList(Allele.NO_CALL);
     private static final int ALLELE_EXTENSION = 2;
+    private static final String phase01 = "0|1";
+    private static final String phase10 = "1|0";
 
     private MergeVariantsAcrossHaplotypes crossHaplotypeEventMerger;
 
@@ -404,14 +406,19 @@ public class HaplotypeCallerGenotypingEngine extends GenotypingEngine<HaplotypeC
                             return 0;
                         }
 
-                        phaseSetMapping.put(call, new Pair<>(uniqueCounter, callIsOnAllHaps ? "1|1" : "0|1"));
-                        phaseSetMapping.put(comp, new Pair<>(uniqueCounter, compIsOnAllHaps ? "1|1" : "0|1"));
+                        // An important note: even for homozygous variants we are setting the phase as "0|1" here.
+                        // We do this because we cannot possibly know for sure at this time that the genotype for this
+                        // sample will actually be homozygous downstream: there are steps in the pipeline that are liable
+                        // to change the genotypes.  Because we can't make those assumptions here, we have decided to output
+                        // the phase as if the call is heterozygous and then "fix" it downstream as needed.
+                        phaseSetMapping.put(call, new Pair<>(uniqueCounter, phase01));
+                        phaseSetMapping.put(comp, new Pair<>(uniqueCounter, phase01));
                         uniqueCounter++;
                     }
                     // otherwise it's part of an existing group so use that group's unique ID
                     else if ( ! phaseSetMapping.containsKey(comp) ) {
                         final Pair<Integer, String> callPhase = phaseSetMapping.get(call);
-                        phaseSetMapping.put(comp, new Pair<>(callPhase.first, compIsOnAllHaps ? "1|1" : callPhase.second));
+                        phaseSetMapping.put(comp, new Pair<>(callPhase.first, callPhase.second));
                     }
                 }
                 // if the variants are apart on *all* haplotypes, record that fact
@@ -431,14 +438,14 @@ public class HaplotypeCallerGenotypingEngine extends GenotypingEngine<HaplotypeC
                                 return 0;
                             }
 
-                            phaseSetMapping.put(call, new Pair<>(uniqueCounter, "0|1"));
-                            phaseSetMapping.put(comp, new Pair<>(uniqueCounter, "1|0"));
+                            phaseSetMapping.put(call, new Pair<>(uniqueCounter, phase01));
+                            phaseSetMapping.put(comp, new Pair<>(uniqueCounter, phase10));
                             uniqueCounter++;
                         }
                         // otherwise it's part of an existing group so use that group's unique ID
                         else if ( ! phaseSetMapping.containsKey(comp) ){
                             final Pair<Integer, String> callPhase = phaseSetMapping.get(call);
-                            phaseSetMapping.put(comp, new Pair<>(callPhase.first, callPhase.second.equals("0|1") ? "1|0" : "0|1"));
+                            phaseSetMapping.put(comp, new Pair<>(callPhase.first, callPhase.second.equals(phase01) ? phase10 : phase01));
                         }
                     }
                 }
diff --git a/protected/gatk-tools-protected/src/main/java/org/broadinstitute/gatk/tools/walkers/variantutils/GenotypeGVCFs.java b/protected/gatk-tools-protected/src/main/java/org/broadinstitute/gatk/tools/walkers/variantutils/GenotypeGVCFs.java
index 6d83bbbf0..16071e84a 100644
--- a/protected/gatk-tools-protected/src/main/java/org/broadinstitute/gatk/tools/walkers/variantutils/GenotypeGVCFs.java
+++ b/protected/gatk-tools-protected/src/main/java/org/broadinstitute/gatk/tools/walkers/variantutils/GenotypeGVCFs.java
@@ -52,6 +52,7 @@ import org.broadinstitute.gatk.tools.walkers.genotyper.GenotypingEngine;
 import org.broadinstitute.gatk.tools.walkers.genotyper.IndexedSampleList;
 import org.broadinstitute.gatk.tools.walkers.genotyper.SampleList;
 import org.broadinstitute.gatk.tools.walkers.genotyper.SampleListUtils;
+import org.broadinstitute.gatk.tools.walkers.haplotypecaller.HaplotypeCaller;
 import org.broadinstitute.gatk.utils.commandline.*;
 import org.broadinstitute.gatk.engine.CommandLineGATK;
 import org.broadinstitute.gatk.engine.arguments.DbsnpArgumentCollection;
@@ -218,15 +219,7 @@ public class GenotypeGVCFs extends RodWalker<VariantContext, VariantContextWrite
                 return null;
 
             regenotypedVC = GATKVariantContextUtils.reverseTrimAlleles(regenotypedVC);
-
-            // we want to carry forward the attributes from the original VC but make sure to add the MLE-based annotations
-            final Map<String, Object> attrs = new HashMap<>(originalVC.getAttributes());
-            attrs.put(VCFConstants.MLE_ALLELE_COUNT_KEY, regenotypedVC.getAttribute(VCFConstants.MLE_ALLELE_COUNT_KEY));
-            attrs.put(VCFConstants.MLE_ALLELE_FREQUENCY_KEY, regenotypedVC.getAttribute(VCFConstants.MLE_ALLELE_FREQUENCY_KEY));
-            if (regenotypedVC.hasAttribute(GenotypingEngine.NUMBER_OF_DISCOVERED_ALLELES_KEY))
-                attrs.put(GenotypingEngine.NUMBER_OF_DISCOVERED_ALLELES_KEY, regenotypedVC.getAttribute(GenotypingEngine.NUMBER_OF_DISCOVERED_ALLELES_KEY));
-
-            result = new VariantContextBuilder(regenotypedVC).attributes(attrs).make();
+            result = addGenotypingAnnotations(originalVC.getAttributes(), regenotypedVC);
         }
 
         // if it turned monomorphic then we either need to ignore or fix such sites
@@ -237,18 +230,47 @@ public class GenotypeGVCFs extends RodWalker<VariantContext, VariantContextWrite
             createRefGTs = true;
         }
 
-        // re-annotate it
-        result = annotationEngine.annotateContext(tracker, ref, null, result);
+        // Re-annotate and fix/remove some of the original annotations.
+        // Note that the order of these actions matters and is different for polymorphic and monomorphic sites.
+        // For polymorphic sites we need to make sure e.g. the SB tag is sent to the annotation engine and then removed later.
+        // For monomorphic sites we need to make sure e.g. the hom ref genotypes are created and only then are passed to the annotation engine.
+        // We could theoretically make 2 passes to re-create the genotypes, but that gets extremely expensive with large sample sizes.
+        if ( createRefGTs ) {
+            result = new VariantContextBuilder(result).genotypes(cleanupGenotypeAnnotations(result, true)).make();
+            result = annotationEngine.annotateContext(tracker, ref, null, result);
+        } else {
+            result = annotationEngine.annotateContext(tracker, ref, null, result);
+            result = new VariantContextBuilder(result).genotypes(cleanupGenotypeAnnotations(result, false)).make();
+        }
 
-        // fix some of the annotations
-        return new VariantContextBuilder(result).genotypes(cleanupGenotypeAnnotations(result, createRefGTs)).make();
+        return result;
     }
 
+    /**
+     * Add genotyping-based annotations to the new VC
+     *
+     * @param originalAttributes the non-null annotations from the original VC
+     * @param newVC the new non-null VC
+     * @return a non-null VC
+     */
+    private VariantContext addGenotypingAnnotations(final Map<String, Object> originalAttributes, final VariantContext newVC) {
+        // we want to carry forward the attributes from the original VC but make sure to add the MLE-based annotations
+        final Map<String, Object> attrs = new HashMap<>(originalAttributes);
+        attrs.put(VCFConstants.MLE_ALLELE_COUNT_KEY, newVC.getAttribute(VCFConstants.MLE_ALLELE_COUNT_KEY));
+        attrs.put(VCFConstants.MLE_ALLELE_FREQUENCY_KEY, newVC.getAttribute(VCFConstants.MLE_ALLELE_FREQUENCY_KEY));
+        if (newVC.hasAttribute(GenotypingEngine.NUMBER_OF_DISCOVERED_ALLELES_KEY))
+            attrs.put(GenotypingEngine.NUMBER_OF_DISCOVERED_ALLELES_KEY, newVC.getAttribute(GenotypingEngine.NUMBER_OF_DISCOVERED_ALLELES_KEY));
+
+        return new VariantContextBuilder(newVC).attributes(attrs).make();
+    }
+
+
     /**
      * Cleans up genotype-level annotations that need to be updated.
      * 1. move MIN_DP to DP if present
      * 2. propagate DP to AD if not present
      * 3. remove SB if present
+     * 4. change the PGT value from "0|1" to "1|1" for homozygous variant genotypes
      *
      * @param VC            the VariantContext with the Genotypes to fix
      * @param createRefGTs  if true we will also create proper hom ref genotypes since we assume the site is monomorphic
@@ -273,6 +295,11 @@ public class GenotypeGVCFs extends RodWalker<VariantContext, VariantContextWrite
             // remove SB
             attrs.remove("SB");
 
+            // update PGT for hom vars
+            if ( oldGT.isHomVar() && oldGT.hasExtendedAttribute(HaplotypeCaller.HAPLOTYPE_CALLER_PHASING_GT_KEY) ) {
+                attrs.put(HaplotypeCaller.HAPLOTYPE_CALLER_PHASING_GT_KEY, "1|1");
+            }
+
             // create AD if it's not there
             if ( !oldGT.hasAD() && VC.isVariant() ) {
                 final int[] AD = new int[VC.getNAlleles()];
diff --git a/protected/gatk-tools-protected/src/test/java/org/broadinstitute/gatk/tools/walkers/haplotypecaller/HaplotypeCallerGVCFIntegrationTest.java b/protected/gatk-tools-protected/src/test/java/org/broadinstitute/gatk/tools/walkers/haplotypecaller/HaplotypeCallerGVCFIntegrationTest.java
index 78d75d92d..6cf7593f6 100644
--- a/protected/gatk-tools-protected/src/test/java/org/broadinstitute/gatk/tools/walkers/haplotypecaller/HaplotypeCallerGVCFIntegrationTest.java
+++ b/protected/gatk-tools-protected/src/test/java/org/broadinstitute/gatk/tools/walkers/haplotypecaller/HaplotypeCallerGVCFIntegrationTest.java
@@ -86,8 +86,8 @@ public class HaplotypeCallerGVCFIntegrationTest extends WalkerTest {
 
         // this functionality can be adapted to provide input data for whatever you might want in your data
         tests.add(new Object[]{NA12878_PCRFREE, ReferenceConfidenceMode.NONE, PCRFreeIntervals, "9db87ae56df22456f3c08024384f3e5e"});
-        tests.add(new Object[]{NA12878_PCRFREE, ReferenceConfidenceMode.BP_RESOLUTION, PCRFreeIntervals, "90dc8950e28e042097817d785022482e"});
-        tests.add(new Object[]{NA12878_PCRFREE, ReferenceConfidenceMode.GVCF, PCRFreeIntervals, "a64e2d8e60a1be9cb0b4306c85e96393"});
+        tests.add(new Object[]{NA12878_PCRFREE, ReferenceConfidenceMode.BP_RESOLUTION, PCRFreeIntervals, "ad0b6274991d451a6491f3118f0e7b2b"});
+        tests.add(new Object[]{NA12878_PCRFREE, ReferenceConfidenceMode.GVCF, PCRFreeIntervals, "956938fd1b5c7bf1b717326a7dd46d91"});
         tests.add(new Object[]{NA12878_WEx, ReferenceConfidenceMode.NONE, WExIntervals, "d5c07fa3edca496a84fd17cecad06230"});
         tests.add(new Object[]{NA12878_WEx, ReferenceConfidenceMode.BP_RESOLUTION, WExIntervals, "66019a0914f905522da6bd3b557a57d1"});
 
diff --git a/protected/gatk-tools-protected/src/test/java/org/broadinstitute/gatk/tools/walkers/haplotypecaller/HaplotypeCallerGenotypingEngineUnitTest.java b/protected/gatk-tools-protected/src/test/java/org/broadinstitute/gatk/tools/walkers/haplotypecaller/HaplotypeCallerGenotypingEngineUnitTest.java
index 11a902b08..e4e189611 100644
--- a/protected/gatk-tools-protected/src/test/java/org/broadinstitute/gatk/tools/walkers/haplotypecaller/HaplotypeCallerGenotypingEngineUnitTest.java
+++ b/protected/gatk-tools-protected/src/test/java/org/broadinstitute/gatk/tools/walkers/haplotypecaller/HaplotypeCallerGenotypingEngineUnitTest.java
@@ -479,11 +479,14 @@ public class HaplotypeCallerGenotypingEngineUnitTest extends BaseTest {
         haplotypeMap.put(vc4, haplotypes24);
         tests.add(new Object[]{calls, new HashMap<>(haplotypeMap), 2, 3, 1, 2, 1});
 
+        // test 2 hets
+        haplotypeMap.remove(vc3);
+        tests.add(new Object[]{Arrays.asList(vc2, vc4), new HashMap<>(haplotypeMap), 1, 2, 1, 2, 0});
+
         // test 2 with opposite phase
         final Set<Haplotype> haplotypes1 = new HashSet<>();
         haplotypes1.add(pos1);
         haplotypeMap.put(vc1, haplotypes1);
-        haplotypeMap.remove(vc3);
         tests.add(new Object[]{Arrays.asList(vc1, vc2, vc4), new HashMap<>(haplotypeMap), 2, 3, 1, 1, 2});
 
         // test homs around a het
@@ -498,7 +501,7 @@ public class HaplotypeCallerGenotypingEngineUnitTest extends BaseTest {
         haplotypeMap.put(vc2, haplotypes2hom);
         haplotypeMap.put(vc3, haplotypes3het);
         haplotypeMap.put(vc4, haplotypes4hom);
-        tests.add(new Object[]{calls, new HashMap<>(haplotypeMap), 2, 3, 1, 1, 0});
+        tests.add(new Object[]{calls, new HashMap<>(haplotypeMap), 2, 3, 1, 3, 0});
 
         // test hets around a hom
         final Set<Haplotype> haplotypes2het = new HashSet<>();
@@ -511,7 +514,7 @@ public class HaplotypeCallerGenotypingEngineUnitTest extends BaseTest {
         haplotypeMap.put(vc2, haplotypes2het);
         haplotypeMap.put(vc3, haplotypes3hom);
         haplotypeMap.put(vc4, haplotypes4het);
-        tests.add(new Object[]{calls, new HashMap<>(haplotypeMap), 2, 3, 1, 2, 0});
+        tests.add(new Object[]{calls, new HashMap<>(haplotypeMap), 2, 3, 1, 3, 0});
 
         // test no phased variants around a hom
         final Set<Haplotype> haplotypes2incomplete = new HashSet<>();
diff --git a/protected/gatk-tools-protected/src/test/java/org/broadinstitute/gatk/tools/walkers/variantutils/GenotypeGVCFsIntegrationTest.java b/protected/gatk-tools-protected/src/test/java/org/broadinstitute/gatk/tools/walkers/variantutils/GenotypeGVCFsIntegrationTest.java
index 158533450..f4ebb596f 100644
--- a/protected/gatk-tools-protected/src/test/java/org/broadinstitute/gatk/tools/walkers/variantutils/GenotypeGVCFsIntegrationTest.java
+++ b/protected/gatk-tools-protected/src/test/java/org/broadinstitute/gatk/tools/walkers/variantutils/GenotypeGVCFsIntegrationTest.java
@@ -61,6 +61,15 @@ public class GenotypeGVCFsIntegrationTest extends WalkerTest {
         return baseTestString(" -V " + privateTestDir + "gvcf.basepairResolution.vcf " + args, b37KGReference);
     }
 
+    @Test(enabled = true)
+    public void testUpdatePGT() {
+        WalkerTestSpec spec = new WalkerTestSpec(
+                baseTestString(" -V " + privateTestDir + "testUpdatePGT.vcf", b37KGReference),
+                1,
+                Arrays.asList("bc3d3eff337836af245b81f52b94d70c"));
+        executeTest("testUpdatePGT", spec);
+    }
+
     @Test(enabled = true)
     public void combineSingleSamplePipelineGVCF() {
         WalkerTestSpec spec = new WalkerTestSpec(
@@ -81,7 +90,7 @@ public class GenotypeGVCFsIntegrationTest extends WalkerTest {
                         " -V:sample3 " + privateTestDir + "combine.single.sample.pipeline.3.vcf" +
                         " --includeNonVariantSites -L 20:10,030,000-10,033,000 -L 20:10,386,000-10,386,500", b37KGReference),
                 1,
-                Arrays.asList("f1dd2b9ab422c0b806392464e466ed91"));
+                Arrays.asList("4193e7c4e6fc889b4aa5a326899b1a4e"));
         executeTest("combineSingleSamplePipelineGVCF_includeNonVariants", spec);
     }