diff --git a/hapi-fhir-base/src/main/java/ca/uhn/fhir/util/FhirTerser.java b/hapi-fhir-base/src/main/java/ca/uhn/fhir/util/FhirTerser.java
index 082daaf122c..44550187d2b 100644
--- a/hapi-fhir-base/src/main/java/ca/uhn/fhir/util/FhirTerser.java
+++ b/hapi-fhir-base/src/main/java/ca/uhn/fhir/util/FhirTerser.java
@@ -230,72 +230,100 @@ public class FhirTerser {
 			}
 
 			// DSTU2
-			List<ExtensionDt> extensionDts = Collections.emptyList();
-			if (theCurrentObj instanceof ISupportsUndeclaredExtensions) {
-				extensionDts = ((ISupportsUndeclaredExtensions) theCurrentObj).getUndeclaredExtensionsByUrl(extensionUrl);
+			if (myContext.getVersion().getVersion().isOlderThan(FhirVersionEnum.DSTU3)) {
+				List<ExtensionDt> extensionDts = Collections.emptyList();
+				if (theCurrentObj instanceof ISupportsUndeclaredExtensions) {
+					extensionDts = ((ISupportsUndeclaredExtensions) theCurrentObj).getUndeclaredExtensionsByUrl(extensionUrl);
 
-				if (extensionDts.isEmpty() && theCreate) {
-					// FIXME: Add a new extension with extensionUrl and null value.
-					// FIXME: Discern between extensions and modifier extensions.
+					if (extensionDts.isEmpty() && theCreate) {
+						// We assume the extension is not a modifier extension.
+						extensionDts = new ArrayList<>(); // Implementation of ISupportsUndeclaredExtensions.getUndeclaredExtensionsByUrl(...) returns unmodifiable list.
+						ExtensionDt extensionDt = ((ISupportsUndeclaredExtensions) theCurrentObj).addUndeclaredExtension(false, extensionUrl);
+						extensionDts.add(extensionDt);
+					}
+				} else if (theCurrentObj instanceof IBaseExtension) {
+					extensionDts = ((IBaseExtension) theCurrentObj).getExtension();
+
+					if (extensionDts.isEmpty() && theCreate) {
+						// We assume the extension is not a modifier extension.
+						ExtensionDt extensionDt = new ExtensionDt();
+						extensionDt.setUrl(extensionUrl);
+						((IBaseExtension) theCurrentObj).getExtension().add(extensionDt);
+						extensionDts.add(extensionDt);
+					}
 				}
-			} else if (theCurrentObj instanceof IBaseExtension) {
-				extensionDts = ((IBaseExtension) theCurrentObj).getExtension();
 
-				if (extensionDts.isEmpty() && theCreate) {
-					// FIXME: Add a new extension with extensionUrl and null value.
+				for (ExtensionDt next : extensionDts) {
+					if (theWantedClass.isAssignableFrom(next.getClass())) {
+						retVal.add((T) next);
+					}
+				}
+			} else {
+				// DSTU3+
+				final String extensionUrlForLambda = extensionUrl;
+				List<IBaseExtension> extensions = Collections.emptyList();
+				if (theCurrentObj instanceof IBaseHasExtensions) {
+					extensions = ((IBaseHasExtensions) theCurrentObj).getExtension()
+						.stream()
+						.filter(t -> t.getUrl().equals(extensionUrlForLambda))
+						.collect(Collectors.toList());
+
+					if (extensions.isEmpty() && theCreate) {
+						IBaseExtension extension = ((IBaseHasExtensions) theCurrentObj).addExtension();
+						extension.setUrl(extensionUrl);
+						extensions.add(extension);
+					}
+				}
+
+				for (IBaseExtension next : extensions) {
+					if (theWantedClass.isAssignableFrom(next.getClass())) {
+						retVal.add((T) next);
+					}
 				}
 			}
 
-			for (ExtensionDt next : extensionDts) {
-				if (theWantedClass.isAssignableFrom(next.getClass())) {
-					retVal.add((T) next);
+			if (theSubList.size() > 1) {
+				List<T> values = retVal;
+				retVal = new ArrayList<>();
+				for (T nextElement : values) {
+					BaseRuntimeElementCompositeDefinition<?> nextChildDef = (BaseRuntimeElementCompositeDefinition<?>) myContext.getElementDefinition((Class<? extends IBase>) nextElement.getClass());
+					List<T> foundValues = getValues(nextChildDef, nextElement, theSubList.subList(1, theSubList.size()), theWantedClass);
+					retVal.addAll(foundValues);
 				}
 			}
 
+			return retVal;
+		}
+
+		if (name.startsWith("modifierExtension('")) {
+			String extensionUrl = name.substring("modifierExtension('".length());
+			int endIndex = extensionUrl.indexOf('\'');
+			if (endIndex != -1) {
+				extensionUrl = extensionUrl.substring(0, endIndex);
+			}
+
 			// DSTU3+
-			final String extensionUrlForLambda = extensionUrl;
-			List<IBaseExtension> extensions = Collections.emptyList();
-			if (theCurrentObj instanceof IBaseHasExtensions) {
-				extensions = ((IBaseHasExtensions) theCurrentObj).getExtension()
-					.stream()
-					.filter(t -> t.getUrl().equals(extensionUrlForLambda))
-					.distinct()
-					.collect(Collectors.toList());
+			if (myContext.getVersion().getVersion().isEqualOrNewerThan(FhirVersionEnum.DSTU3)) {
+				final String extensionUrlForLambda = extensionUrl;
+				List<IBaseExtension> extensions = Collections.emptyList();
 
-				if (extensions.isEmpty() && theCreate) {
-					IBaseExtension extension = ((IBaseHasExtensions) theCurrentObj).addExtension();
-					extension.setUrl(extensionUrl);
-					extensions.add(extension);
+				if (theCurrentObj instanceof IBaseHasModifierExtensions) {
+					extensions = ((IBaseHasModifierExtensions) theCurrentObj).getModifierExtension()
+						.stream()
+						.filter(t -> t.getUrl().equals(extensionUrlForLambda))
+						.collect(Collectors.toList());
+
+					if (extensions.isEmpty() && theCreate) {
+						IBaseExtension modifierExtension = ((IBaseHasModifierExtensions) theCurrentObj).addModifierExtension();
+						modifierExtension.setUrl(extensionUrl);
+						extensions.add(modifierExtension);
+					}
 				}
-			}
-//			List<IBaseExtension> modifierExtensions = Collections.emptyList();
-//			if (theCurrentObj instanceof IBaseHasModifierExtensions) {
-//				modifierExtensions = ((IBaseHasModifierExtensions) theCurrentObj).getModifierExtension()
-//					.stream()
-//					.filter(t -> t.getUrl().equals(extensionUrlForLambda))
-//					.collect(Collectors.toList());
-//
-//				if (modifierExtensions.isEmpty() && theCreate) {
-//					IBaseExtension modifierExtension = ((IBaseHasModifierExtensions) theCurrentObj).addModifierExtension();
-//					modifierExtension.setUrl(extensionUrl);
-//					modifierExtensions.add(modifierExtension);
-//				}
-//			}
-//
-//			List<IBaseExtension> allExtensions = Stream.of(extensions, modifierExtensions)
-//				.flatMap(Collection::stream)
-//				.distinct()
-//				.collect(Collectors.toList());
-//
-//			for (IBaseExtension next : allExtensions) {
-//				if (theWantedClass.isAssignableFrom(next.getClass())) {
-//					retVal.add((T) next);
-//				}
-//			}
 
-			for (IBaseExtension next : extensions) {
-				if (theWantedClass.isAssignableFrom(next.getClass())) {
-					retVal.add((T) next);
+				for (IBaseExtension next : extensions) {
+					if (theWantedClass.isAssignableFrom(next.getClass())) {
+						retVal.add((T) next);
+					}
 				}
 			}
 
@@ -360,24 +388,74 @@ public class FhirTerser {
 		return retVal;
 	}
 
+	/**
+	 * Returns values stored in an element identified by its path. The list of values is of
+	 * type {@link Object}.
+	 *
+	 * <p>Note: this method does not support creation of null-valued modifier extensions for
+	 * versions of FHIR prior to DSTU3.</p>
+	 *
+	 * @param theResource The resource instance to be accessed. Must not be null.
+	 * @param thePath The path for the element to be accessed.
+	 * @return A list of values of type {@link Object}.
+	 */
 	public List<Object> getValues(IBaseResource theResource, String thePath) {
 		Class<Object> wantedClass = Object.class;
 
 		return getValues(theResource, thePath, wantedClass);
 	}
 
+	/**
+	 * Returns values stored in an element identified by its path. The list of values is of
+	 * type {@link Object}.
+	 *
+	 * <p>Note: this method does not support creation of null-valued modifier extensions for
+	 * versions of FHIR prior to DSTU3.</p>
+	 *
+	 * @param theResource The resource instance to be accessed. Must not be null.
+	 * @param thePath The path for the element to be accessed.
+	 * @param theCreate When set to <code>true</code>, the terser will create a null-valued element where none exists.
+	 * @return A list of values of type {@link Object}.
+	 */
 	public List<Object> getValues(IBaseResource theResource, String thePath, boolean theCreate) {
 		Class<Object> wantedClass = Object.class;
 
 		return getValues(theResource, thePath, wantedClass, theCreate);
 	}
 
+	/**
+	 * Returns values stored in an element identified by its path. The list of values is of
+	 * type <code>theWantedClass</code>.
+	 *
+	 * <p>Note: this method does not support creation of null-valued modifier extensions for
+	 * versions of FHIR prior to DSTU3.</p>
+	 *
+	 * @param theResource The resource instance to be accessed. Must not be null.
+	 * @param thePath The path for the element to be accessed.
+	 * @param theWantedClass The desired class to be returned in a list.
+	 * @param <T> Type declared by <code>theWantedClass</code>
+	 * @return A list of values of type <code>theWantedClass</code>.
+	 */
 	public <T> List<T> getValues(IBaseResource theResource, String thePath, Class<T> theWantedClass) {
 		RuntimeResourceDefinition def = myContext.getResourceDefinition(theResource);
 		List<String> parts = parsePath(def, thePath);
 		return getValues(def, theResource, parts, theWantedClass);
 	}
 
+	/**
+	 * Returns values stored in an element identified by its path. The list of values is of
+	 * type <code>theWantedClass</code>.
+	 *
+	 * <p>Note: this method does not support creation of null-valued modifier extensions for
+	 * versions of FHIR prior to DSTU3.</p>
+	 *
+	 * @param theResource The resource instance to be accessed. Must not be null.
+	 * @param thePath The path for the element to be accessed.
+	 * @param theWantedClass The desired class to be returned in a list.
+	 * @param theCreate When set to <code>true</code>, the terser will create a null-valued element where none exists.
+	 * @param <T> Type declared by <code>theWantedClass</code>
+	 * @return A list of values of type <code>theWantedClass</code>.
+	 */
 	public <T> List<T> getValues(IBaseResource theResource, String thePath, Class<T> theWantedClass, boolean theCreate) {
 		RuntimeResourceDefinition def = myContext.getResourceDefinition(theResource);
 		List<String> parts = parsePath(def, thePath);
diff --git a/hapi-fhir-structures-dstu2/src/test/java/ca/uhn/fhir/util/FhirTerserDstu2Test.java b/hapi-fhir-structures-dstu2/src/test/java/ca/uhn/fhir/util/FhirTerserDstu2Test.java
index d4816152d0a..0139b2d6b13 100644
--- a/hapi-fhir-structures-dstu2/src/test/java/ca/uhn/fhir/util/FhirTerserDstu2Test.java
+++ b/hapi-fhir-structures-dstu2/src/test/java/ca/uhn/fhir/util/FhirTerserDstu2Test.java
@@ -1,24 +1,5 @@
 package ca.uhn.fhir.util;
 
-import static org.hamcrest.Matchers.containsInAnyOrder;
-import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertSame;
-import static org.junit.Assert.assertThat;
-import static org.junit.Assert.assertTrue;
-import static org.junit.Assert.fail;
-import static org.mockito.Mockito.mock;
-import static org.mockito.Mockito.when;
-
-import java.lang.reflect.ParameterizedType;
-import java.lang.reflect.Type;
-import java.util.List;
-
-import org.hl7.fhir.instance.model.api.IBase;
-import org.hl7.fhir.instance.model.api.IBaseReference;
-import org.junit.AfterClass;
-import org.junit.Test;
-import org.mockito.ArgumentCaptor;
-
 import ca.uhn.fhir.context.BaseRuntimeChildDefinition;
 import ca.uhn.fhir.context.BaseRuntimeElementDefinition;
 import ca.uhn.fhir.context.FhirContext;
@@ -31,9 +12,26 @@ import ca.uhn.fhir.model.dstu2.resource.Bundle;
 import ca.uhn.fhir.model.dstu2.resource.Observation;
 import ca.uhn.fhir.model.dstu2.resource.Organization;
 import ca.uhn.fhir.model.dstu2.resource.Patient;
+import ca.uhn.fhir.model.primitive.BooleanDt;
 import ca.uhn.fhir.model.primitive.MarkdownDt;
 import ca.uhn.fhir.model.primitive.StringDt;
 import ca.uhn.fhir.parser.DataFormatException;
+import org.hl7.fhir.instance.model.api.IBase;
+import org.hl7.fhir.instance.model.api.IBaseExtension;
+import org.hl7.fhir.instance.model.api.IBaseReference;
+import org.hl7.fhir.instance.model.api.IPrimitiveType;
+import org.junit.AfterClass;
+import org.junit.Test;
+import org.mockito.ArgumentCaptor;
+
+import java.lang.reflect.ParameterizedType;
+import java.lang.reflect.Type;
+import java.util.List;
+
+import static org.hamcrest.Matchers.containsInAnyOrder;
+import static org.junit.Assert.*;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
 
 public class FhirTerserDstu2Test {
 
@@ -180,6 +178,215 @@ public class FhirTerserDstu2Test {
 		assertEquals(1, refs.size());
 		assertSame(ref, refs.get(0));
 	}
+
+	@Test
+	public void testGetValues() {
+		Patient p = new Patient();
+		p.setActive(true);
+		p.addUndeclaredExtension(false, "http://acme.org/extension", new StringDt("value"));
+		p.addUndeclaredExtension(false, "http://acme.org/otherExtension", new StringDt("otherValue"));
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		List<Object> values = ourCtx.newTerser().getValues(p, "Patient.active");
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof IPrimitiveType);
+		assertTrue(values.get(0) instanceof BooleanDt);
+		assertTrue(((BooleanDt) values.get(0)).getValue());
+
+		values = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/extension')");
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof IBaseExtension);
+		assertTrue(values.get(0) instanceof ExtensionDt);
+		assertEquals("http://acme.org/extension", ((ExtensionDt) values.get(0)).getUrl());
+		assertEquals("value", ((StringDt) ((ExtensionDt) values.get(0)).getValue()).getValueAsString());
+	}
+
+	@Test
+	public void testGetValuesAndModify() {
+		Patient p = new Patient();
+		p.setActive(true);
+		p.addUndeclaredExtension(false, "http://acme.org/extension", new StringDt("value"));
+		p.addUndeclaredExtension(false, "http://acme.org/otherExtension", new StringDt("otherValue"));
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		List<Object> values = ourCtx.newTerser().getValues(p, "Patient.active");
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof IPrimitiveType);
+		assertTrue(values.get(0) instanceof BooleanDt);
+		assertTrue(((BooleanDt) values.get(0)).getValue());
+
+		((BooleanDt) values.get(0)).setValue(Boolean.FALSE);
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		values = ourCtx.newTerser().getValues(p, "Patient.active");
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof IPrimitiveType);
+		assertTrue(values.get(0) instanceof BooleanDt);
+		assertFalse(((BooleanDt) values.get(0)).getValue());
+
+		values = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/extension')");
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof IBaseExtension);
+		assertTrue(values.get(0) instanceof ExtensionDt);
+		assertEquals("http://acme.org/extension", ((ExtensionDt) values.get(0)).getUrl());
+		assertEquals("value", ((StringDt) ((ExtensionDt) values.get(0)).getValue()).getValueAsString());
+
+		((ExtensionDt) values.get(0)).setValue(new StringDt("modifiedValue"));
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		values = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/extension')");
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof IBaseExtension);
+		assertTrue(values.get(0) instanceof ExtensionDt);
+		assertEquals("http://acme.org/extension", ((ExtensionDt) values.get(0)).getUrl());
+		assertEquals("modifiedValue", ((StringDt) ((ExtensionDt) values.get(0)).getValue()).getValueAsString());
+	}
+
+	@Test
+	public void testGetValuesMultiple() {
+		Patient p = new Patient();
+		p.addUndeclaredExtension(false, "http://acme.org/extension", new StringDt("value1"));
+		p.addUndeclaredExtension(false, "http://acme.org/extension", new StringDt("value2"));
+		p.addUndeclaredExtension(false, "http://acme.org/otherExtension", new StringDt("otherValue"));
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		List<Object> values = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/extension')");
+		assertEquals(2, values.size());
+		assertTrue(values.get(0) instanceof IBaseExtension);
+		assertTrue(values.get(0) instanceof ExtensionDt);
+		assertEquals("http://acme.org/extension", ((ExtensionDt) values.get(0)).getUrl());
+		assertEquals("value1", ((StringDt) ((ExtensionDt) values.get(0)).getValue()).getValueAsString());
+		assertTrue(values.get(1) instanceof IBaseExtension);
+		assertTrue(values.get(1) instanceof ExtensionDt);
+		assertEquals("http://acme.org/extension", ((ExtensionDt) values.get(1)).getUrl());
+		assertEquals("value2", ((StringDt) ((ExtensionDt) values.get(1)).getValue()).getValueAsString());
+	}
+
+	@Test
+	public void testGetValuesWithWantedClass() {
+		Patient p = new Patient();
+		p.setActive(true);
+		p.addUndeclaredExtension(false, "http://acme.org/extension", new StringDt("value"));
+		p.addUndeclaredExtension(false, "http://acme.org/otherExtension", new StringDt("otherValue"));
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		List<IPrimitiveType> values = ourCtx.newTerser().getValues(p, "Patient.active", IPrimitiveType.class);
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof BooleanDt);
+		assertTrue(((BooleanDt) values.get(0)).getValue());
+
+		List<ExtensionDt> extValues = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/extension')", ExtensionDt.class);
+		assertEquals(1, extValues.size());
+		assertTrue(extValues.get(0).getValue() instanceof StringDt);
+		assertEquals("http://acme.org/extension", extValues.get(0).getUrl());
+		assertEquals("value", ((StringDt) (extValues.get(0).getValue())).getValueAsString());
+	}
+
+	@Test
+	public void testGetValuesWithWantedClassAndModify() {
+		Patient p = new Patient();
+		p.setActive(true);
+		p.addUndeclaredExtension(false, "http://acme.org/extension", new StringDt("value"));
+		p.addUndeclaredExtension(false, "http://acme.org/otherExtension", new StringDt("otherValue"));
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		List<IPrimitiveType> values = ourCtx.newTerser().getValues(p, "Patient.active", IPrimitiveType.class);
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof BooleanDt);
+		assertTrue(((BooleanDt) values.get(0)).getValue());
+
+		((BooleanDt) values.get(0)).setValue(Boolean.FALSE);
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		values = ourCtx.newTerser().getValues(p, "Patient.active", IPrimitiveType.class);
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof BooleanDt);
+		assertFalse(((BooleanDt) values.get(0)).getValue());
+
+		List<ExtensionDt> extValues = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/extension')", ExtensionDt.class);
+		assertEquals(1, extValues.size());
+		assertTrue(extValues.get(0).getValue() instanceof StringDt);
+		assertEquals("http://acme.org/extension", extValues.get(0).getUrl());
+		assertEquals("value", ((StringDt) (extValues.get(0).getValue())).getValueAsString());
+
+		extValues.get(0).setValue(new StringDt("modifiedValue"));
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		extValues = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/extension')", ExtensionDt.class);
+		assertEquals(1, extValues.size());
+		assertTrue(extValues.get(0).getValue() instanceof StringDt);
+		assertEquals("http://acme.org/extension", extValues.get(0).getUrl());
+		assertEquals("modifiedValue", ((StringDt) (extValues.get(0).getValue())).getValueAsString());
+	}
+
+	@Test
+	public void testGetValuesWithWantedClassAndTheCreate() {
+		Patient p = new Patient();
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		List<IPrimitiveType> values = ourCtx.newTerser().getValues(p, "Patient.active", IPrimitiveType.class, true);
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof BooleanDt);
+		assertNull(((BooleanDt) values.get(0)).getValue());
+
+		List<ExtensionDt> extValues = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/extension')", ExtensionDt.class, true);
+		assertEquals(1, extValues.size());
+		assertEquals("http://acme.org/extension", extValues.get(0).getUrl());
+		assertNull(extValues.get(0).getValue());
+	}
+
+	@Test
+	public void testGetValuesWithTheCreate() {
+		Patient p = new Patient();
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		List<Object> values = ourCtx.newTerser().getValues(p, "Patient.active", true);
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof IPrimitiveType);
+		assertTrue(values.get(0) instanceof BooleanDt);
+		assertNull(((BooleanDt) values.get(0)).getValue());
+
+		values = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/extension')", true);
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof IBaseExtension);
+		assertTrue(values.get(0) instanceof ExtensionDt);
+		assertEquals("http://acme.org/extension", ((ExtensionDt) values.get(0)).getUrl());
+		assertNull(((ExtensionDt) values.get(0)).getValue());
+	}
+
+	@Test
+	public void testGetValuesWithTheCreateAndNoOverwrite() {
+		Patient p = new Patient();
+		p.setActive(true);
+		p.addUndeclaredExtension(false, "http://acme.org/extension", new StringDt("value"));
+		p.addUndeclaredExtension(false, "http://acme.org/otherExtension", new StringDt("otherValue"));
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		List<Object> values = ourCtx.newTerser().getValues(p, "Patient.active", true);
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof IPrimitiveType);
+		assertTrue(values.get(0) instanceof BooleanDt);
+		assertTrue(((BooleanDt) values.get(0)).getValue());
+
+		values = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/extension')");
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof IBaseExtension);
+		assertTrue(values.get(0) instanceof ExtensionDt);
+		assertEquals("http://acme.org/extension", ((ExtensionDt) values.get(0)).getUrl());
+		assertEquals("value", ((StringDt) ((ExtensionDt) values.get(0)).getValue()).getValueAsString());
+	}
 	
 	@Test
 	public void testVisitWithModelVisitor2() {
diff --git a/hapi-fhir-structures-dstu3/src/test/java/ca/uhn/fhir/util/FhirTerserDstu3Test.java b/hapi-fhir-structures-dstu3/src/test/java/ca/uhn/fhir/util/FhirTerserDstu3Test.java
index 2cdfcba8030..bf0ffde4ee0 100644
--- a/hapi-fhir-structures-dstu3/src/test/java/ca/uhn/fhir/util/FhirTerserDstu3Test.java
+++ b/hapi-fhir-structures-dstu3/src/test/java/ca/uhn/fhir/util/FhirTerserDstu3Test.java
@@ -179,9 +179,9 @@ public class FhirTerserDstu3Test {
 		p.addExtension()
 			.setUrl("http://acme.org/otherExtension")
 			.setValue(new StringType("otherValue"));
-//		p.addModifierExtension()
-//			.setUrl("http://acme.org/extension")
-//			.setValue(new StringType("modifierValue"));
+		p.addModifierExtension()
+			.setUrl("http://acme.org/modifierExtension")
+			.setValue(new StringType("modifierValue"));
 
 		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
 
@@ -198,12 +198,12 @@ public class FhirTerserDstu3Test {
 		assertEquals("http://acme.org/extension", ((Extension) values.get(0)).getUrl());
 		assertEquals("value", ((StringType) ((Extension) values.get(0)).getValue()).getValueAsString());
 
-//		values = ourCtx.newTerser().getValues(p, "Patient.modifierExtension('http://acme.org/extension')");
-//		assertEquals(1, values.size());
-//		assertTrue(values.get(0) instanceof IBaseExtension);
-//		assertTrue(values.get(0) instanceof Extension);
-//		assertEquals("http://acme.org/extension", ((Extension) values.get(0)).getUrl());
-//		assertEquals("value", ((StringType) ((Extension) values.get(0)).getValue()).getValueAsString());
+		values = ourCtx.newTerser().getValues(p, "Patient.modifierExtension('http://acme.org/modifierExtension')");
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof IBaseExtension);
+		assertTrue(values.get(0) instanceof Extension);
+		assertEquals("http://acme.org/modifierExtension", ((Extension) values.get(0)).getUrl());
+		assertEquals("modifierValue", ((StringType) ((Extension) values.get(0)).getValue()).getValueAsString());
 	}
 
 	@Test
@@ -216,6 +216,9 @@ public class FhirTerserDstu3Test {
 		p.addExtension()
 			.setUrl("http://acme.org/otherExtension")
 			.setValue(new StringType("otherValue"));
+		p.addModifierExtension()
+			.setUrl("http://acme.org/modifierExtension")
+			.setValue(new StringType("modifierValue"));
 
 		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
 
@@ -252,6 +255,68 @@ public class FhirTerserDstu3Test {
 		assertTrue(values.get(0) instanceof Extension);
 		assertEquals("http://acme.org/extension", ((Extension) values.get(0)).getUrl());
 		assertEquals("modifiedValue", ((StringType) ((Extension) values.get(0)).getValue()).getValueAsString());
+
+		values = ourCtx.newTerser().getValues(p, "Patient.modifierExtension('http://acme.org/modifierExtension')");
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof IBaseExtension);
+		assertTrue(values.get(0) instanceof Extension);
+		assertEquals("http://acme.org/modifierExtension", ((Extension) values.get(0)).getUrl());
+		assertEquals("modifierValue", ((StringType) ((Extension) values.get(0)).getValue()).getValueAsString());
+
+		((Extension) values.get(0)).setValue(new StringType("modifiedModifierValue"));
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		values = ourCtx.newTerser().getValues(p, "Patient.modifierExtension('http://acme.org/modifierExtension')");
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof IBaseExtension);
+		assertTrue(values.get(0) instanceof Extension);
+		assertEquals("http://acme.org/modifierExtension", ((Extension) values.get(0)).getUrl());
+		assertEquals("modifiedModifierValue", ((StringType) ((Extension) values.get(0)).getValue()).getValueAsString());
+	}
+
+	@Test
+	public void testGetValuesMultiple() {
+		Patient p = new Patient();
+		p.addExtension()
+			.setUrl("http://acme.org/extension")
+			.setValue(new StringType("value1"));
+		p.addExtension()
+			.setUrl("http://acme.org/extension")
+			.setValue(new StringType("value2"));
+		p.addExtension()
+			.setUrl("http://acme.org/otherExtension")
+			.setValue(new StringType("otherValue"));
+		p.addModifierExtension()
+			.setUrl("http://acme.org/modifierExtension")
+			.setValue(new StringType("modifierValue1"));
+		p.addModifierExtension()
+			.setUrl("http://acme.org/modifierExtension")
+			.setValue(new StringType("modifierValue2"));
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		List<Object> values = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/extension')");
+		assertEquals(2, values.size());
+		assertTrue(values.get(0) instanceof IBaseExtension);
+		assertTrue(values.get(0) instanceof Extension);
+		assertEquals("http://acme.org/extension", ((Extension) values.get(0)).getUrl());
+		assertEquals("value1", ((StringType) ((Extension) values.get(0)).getValue()).getValueAsString());
+		assertTrue(values.get(1) instanceof IBaseExtension);
+		assertTrue(values.get(1) instanceof Extension);
+		assertEquals("http://acme.org/extension", ((Extension) values.get(1)).getUrl());
+		assertEquals("value2", ((StringType) ((Extension) values.get(1)).getValue()).getValueAsString());
+
+		values = ourCtx.newTerser().getValues(p, "Patient.modifierExtension('http://acme.org/modifierExtension')");
+		assertEquals(2, values.size());
+		assertTrue(values.get(0) instanceof IBaseExtension);
+		assertTrue(values.get(0) instanceof Extension);
+		assertEquals("http://acme.org/modifierExtension", ((Extension) values.get(0)).getUrl());
+		assertEquals("modifierValue1", ((StringType) ((Extension) values.get(0)).getValue()).getValueAsString());
+		assertTrue(values.get(1) instanceof IBaseExtension);
+		assertTrue(values.get(1) instanceof Extension);
+		assertEquals("http://acme.org/modifierExtension", ((Extension) values.get(1)).getUrl());
+		assertEquals("modifierValue2", ((StringType) ((Extension) values.get(1)).getValue()).getValueAsString());
 	}
 
 	@Test
@@ -264,6 +329,9 @@ public class FhirTerserDstu3Test {
 		p.addExtension()
 			.setUrl("http://acme.org/otherExtension")
 			.setValue(new StringType("otherValue"));
+		p.addModifierExtension()
+			.setUrl("http://acme.org/modifierExtension")
+			.setValue(new StringType("modifierValue"));
 
 		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
 
@@ -277,6 +345,12 @@ public class FhirTerserDstu3Test {
 		assertTrue(extValues.get(0).getValue() instanceof StringType);
 		assertEquals("http://acme.org/extension", extValues.get(0).getUrl());
 		assertEquals("value", ((StringType) (extValues.get(0).getValue())).getValueAsString());
+
+		extValues = ourCtx.newTerser().getValues(p, "Patient.modifierExtension('http://acme.org/modifierExtension')", Extension.class);
+		assertEquals(1, extValues.size());
+		assertTrue(extValues.get(0).getValue() instanceof StringType);
+		assertEquals("http://acme.org/modifierExtension", extValues.get(0).getUrl());
+		assertEquals("modifierValue", ((StringType) (extValues.get(0).getValue())).getValueAsString());
 	}
 
 	@Test
@@ -289,6 +363,9 @@ public class FhirTerserDstu3Test {
 		p.addExtension()
 			.setUrl("http://acme.org/otherExtension")
 			.setValue(new StringType("otherValue"));
+		p.addModifierExtension()
+			.setUrl("http://acme.org/modifierExtension")
+			.setValue(new StringType("modifierValue"));
 
 		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
 
@@ -321,6 +398,22 @@ public class FhirTerserDstu3Test {
 		assertTrue(extValues.get(0).getValue() instanceof StringType);
 		assertEquals("http://acme.org/extension", extValues.get(0).getUrl());
 		assertEquals("modifiedValue", ((StringType) (extValues.get(0).getValue())).getValueAsString());
+
+		extValues = ourCtx.newTerser().getValues(p, "Patient.modifierExtension('http://acme.org/modifierExtension')", Extension.class);
+		assertEquals(1, extValues.size());
+		assertTrue(extValues.get(0).getValue() instanceof StringType);
+		assertEquals("http://acme.org/modifierExtension", extValues.get(0).getUrl());
+		assertEquals("modifierValue", ((StringType) (extValues.get(0).getValue())).getValueAsString());
+
+		extValues.get(0).setValue(new StringType("modifiedModifierValue"));
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		extValues = ourCtx.newTerser().getValues(p, "Patient.modifierExtension('http://acme.org/modifierExtension')", Extension.class);
+		assertEquals(1, extValues.size());
+		assertTrue(extValues.get(0).getValue() instanceof StringType);
+		assertEquals("http://acme.org/modifierExtension", extValues.get(0).getUrl());
+		assertEquals("modifiedModifierValue", ((StringType) (extValues.get(0).getValue())).getValueAsString());
 	}
 
 	@Test
@@ -338,6 +431,11 @@ public class FhirTerserDstu3Test {
 		assertEquals(1, extValues.size());
 		assertEquals("http://acme.org/extension", extValues.get(0).getUrl());
 		assertNull(extValues.get(0).getValue());
+
+		extValues = ourCtx.newTerser().getValues(p, "Patient.modifierExtension('http://acme.org/modifierExtension')", Extension.class, true);
+		assertEquals(1, extValues.size());
+		assertEquals("http://acme.org/modifierExtension", extValues.get(0).getUrl());
+		assertNull(extValues.get(0).getValue());
 	}
 
 	@Test
@@ -358,6 +456,13 @@ public class FhirTerserDstu3Test {
 		assertTrue(values.get(0) instanceof Extension);
 		assertEquals("http://acme.org/extension", ((Extension) values.get(0)).getUrl());
 		assertNull(((Extension) values.get(0)).getValue());
+
+		values = ourCtx.newTerser().getValues(p, "Patient.modifierExtension('http://acme.org/modifierExtension')", true);
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof IBaseExtension);
+		assertTrue(values.get(0) instanceof Extension);
+		assertEquals("http://acme.org/modifierExtension", ((Extension) values.get(0)).getUrl());
+		assertNull(((Extension) values.get(0)).getValue());
 	}
 
 	@Test
@@ -370,6 +475,9 @@ public class FhirTerserDstu3Test {
 		p.addExtension()
 			.setUrl("http://acme.org/otherExtension")
 			.setValue(new StringType("otherValue"));
+		p.addModifierExtension()
+			.setUrl("http://acme.org/modifierExtension")
+			.setValue(new StringType("modifierValue"));
 
 		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
 
@@ -385,6 +493,13 @@ public class FhirTerserDstu3Test {
 		assertTrue(values.get(0) instanceof Extension);
 		assertEquals("http://acme.org/extension", ((Extension) values.get(0)).getUrl());
 		assertEquals("value", ((StringType) ((Extension) values.get(0)).getValue()).getValueAsString());
+
+		values = ourCtx.newTerser().getValues(p, "Patient.modifierExtension('http://acme.org/modifierExtension')");
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof IBaseExtension);
+		assertTrue(values.get(0) instanceof Extension);
+		assertEquals("http://acme.org/modifierExtension", ((Extension) values.get(0)).getUrl());
+		assertEquals("modifierValue", ((StringType) ((Extension) values.get(0)).getValue()).getValueAsString());
 	}
 
 	@Test