diff --git a/hapi-fhir-server-mdm/src/main/java/ca/uhn/fhir/mdm/util/TerserUtil.java b/hapi-fhir-server-mdm/src/main/java/ca/uhn/fhir/mdm/util/TerserUtil.java
index 88c75228246..d6515f7e159 100644
--- a/hapi-fhir-server-mdm/src/main/java/ca/uhn/fhir/mdm/util/TerserUtil.java
+++ b/hapi-fhir-server-mdm/src/main/java/ca/uhn/fhir/mdm/util/TerserUtil.java
@@ -190,6 +190,10 @@ public final class TerserUtil {
 		return definition.getChildByName(theFieldName) != null;
 	}
 
+	public static void replaceField(FhirContext theFhirContext, String theFieldName, IBaseResource theFrom, IBaseResource theTo) {
+		replaceField(theFhirContext, theFhirContext.newTerser(), theFieldName, theFrom, theTo);
+	}
+
 	public static void replaceField(FhirContext theFhirContext, FhirTerser theTerser, String theFieldName, IBaseResource theFrom, IBaseResource theTo) {
 		replaceField(theFrom, theTo, getBaseRuntimeChildDefinition(theFhirContext, theFieldName, theFrom));
 	}
@@ -221,6 +225,19 @@ public final class TerserUtil {
 		}
 	}
 
+	/**
+	 * Merges value of the specified field from theFrom resource to theTo resource. Fields values are compared via
+	 * the equalsDeep method, or via object identity if this method is not available.
+	 *
+	 * @param theFhirContext
+	 * @param theFieldName
+	 * @param theFrom
+	 * @param theTo
+	 */
+	public static void mergeField(FhirContext theFhirContext, String theFieldName, IBaseResource theFrom, IBaseResource theTo) {
+		mergeField(theFhirContext, theFhirContext.newTerser(), theFieldName, theFrom, theTo);
+	}
+
 	/**
 	 * Merges value of the specified field from theFrom resource to theTo resource. Fields values are compared via
 	 * the equalsDeep method, or via object identity if this method is not available.
diff --git a/hapi-fhir-server-mdm/src/test/java/ca/uhn/fhir/mdm/util/TerserUtilTest.java b/hapi-fhir-server-mdm/src/test/java/ca/uhn/fhir/mdm/util/TerserUtilTest.java
index c0eb2a2b09a..338fe934024 100644
--- a/hapi-fhir-server-mdm/src/test/java/ca/uhn/fhir/mdm/util/TerserUtilTest.java
+++ b/hapi-fhir-server-mdm/src/test/java/ca/uhn/fhir/mdm/util/TerserUtilTest.java
@@ -2,13 +2,18 @@ package ca.uhn.fhir.mdm.util;
 
 import ca.uhn.fhir.context.RuntimeResourceDefinition;
 import ca.uhn.fhir.mdm.BaseR4Test;
+import org.hl7.fhir.r4.model.DateTimeType;
+import org.hl7.fhir.r4.model.Extension;
 import org.hl7.fhir.r4.model.Identifier;
 import org.hl7.fhir.r4.model.Patient;
 import org.junit.jupiter.api.Test;
 
 import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.Matchers.hasSize;
-import static org.junit.jupiter.api.Assertions.*;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertNull;
+import static org.junit.jupiter.api.Assertions.assertTrue;
 
 class TerserUtilTest extends BaseR4Test {
 
@@ -69,6 +74,101 @@ class TerserUtilTest extends BaseR4Test {
 		assertThat(p2.getName().get(1).getGiven(), hasSize(2));
 	}
 
+	@Test
+	void testMergeForAddressWithExtensions() {
+		Extension ext = new Extension();
+		ext.setUrl("http://hapifhir.io/extensions/address#create-timestamp");
+		ext.setValue(new DateTimeType("2021-01-02T11:13:15"));
+
+		Patient p1 = new Patient();
+		p1.addAddress()
+			.addLine("10 Main Street")
+			.setCity("Hamilton")
+			.setState("ON")
+			.setPostalCode("Z0Z0Z0")
+			.setCountry("Canada")
+			.addExtension(ext);
+
+		Patient p2 = new Patient();
+		p2.addAddress().addLine("10 Lenin Street").setCity("Severodvinsk").setCountry("Russia");
+
+		TerserUtil.mergeField(ourFhirContext,"address", p1, p2);
+
+		assertEquals(2, p2.getAddress().size());
+		assertEquals("[10 Lenin Street]", p2.getAddress().get(0).getLine().toString());
+		assertEquals("[10 Main Street]", p2.getAddress().get(1).getLine().toString());
+		assertTrue(p2.getAddress().get(1).hasExtension());
+
+		p1 = new Patient();
+		p1.addAddress().addLine("10 Main Street").addExtension(ext);
+		p2 = new Patient();
+		p2.addAddress().addLine("10 Main Street").addExtension(new Extension("demo", new DateTimeType("2021-01-02")));
+
+		TerserUtil.mergeField(ourFhirContext,"address", p1, p2);
+		assertEquals(2, p2.getAddress().size());
+		assertTrue(p2.getAddress().get(0).hasExtension());
+		assertTrue(p2.getAddress().get(1).hasExtension());
+
+	}
+
+	@Test
+	void testReplaceForAddressWithExtensions() {
+		Extension ext = new Extension();
+		ext.setUrl("http://hapifhir.io/extensions/address#create-timestamp");
+		ext.setValue(new DateTimeType("2021-01-02T11:13:15"));
+
+		Patient p1 = new Patient();
+		p1.addAddress()
+			.addLine("10 Main Street")
+			.setCity("Hamilton")
+			.setState("ON")
+			.setPostalCode("Z0Z0Z0")
+			.setCountry("Canada")
+			.addExtension(ext);
+
+		Patient p2 = new Patient();
+		p2.addAddress().addLine("10 Lenin Street").setCity("Severodvinsk").setCountry("Russia");
+
+		TerserUtil.replaceField(ourFhirContext,"address", p1, p2);
+
+		assertEquals(1, p2.getAddress().size());
+		assertEquals("[10 Main Street]", p2.getAddress().get(0).getLine().toString());
+		assertTrue(p2.getAddress().get(0).hasExtension());
+	}
+
+	@Test
+	void testMergeForSimilarAddresses() {
+		Extension ext = new Extension();
+		ext.setUrl("http://hapifhir.io/extensions/address#create-timestamp");
+		ext.setValue(new DateTimeType("2021-01-02T11:13:15"));
+
+		Patient p1 = new Patient();
+		p1.addAddress()
+			.addLine("10 Main Street")
+			.setCity("Hamilton")
+			.setState("ON")
+			.setPostalCode("Z0Z0Z0")
+			.setCountry("Canada")
+			.addExtension(ext);
+
+		Patient p2 = new Patient();
+		p2.addAddress()
+			.addLine("10 Main Street")
+			.setCity("Hamilton")
+			.setState("ON")
+			.setPostalCode("Z0Z0Z1")
+			.setCountry("Canada")
+			.addExtension(ext);
+
+		TerserUtil.mergeField(ourFhirContext,"address", p1, p2);
+
+		assertEquals(2, p2.getAddress().size());
+		assertEquals("[10 Main Street]", p2.getAddress().get(0).getLine().toString());
+		assertEquals("[10 Main Street]", p2.getAddress().get(1).getLine().toString());
+		assertTrue(p2.getAddress().get(1).hasExtension());
+	}
+
+
 	@Test
 	void testCloneWithDuplicateNonPrimitives() {
 		Patient p1 = new Patient();