diff --git a/hapi-fhir-structures-r4/src/main/java/org/hl7/fhir/r4/hapi/fluentpath/FhirPathR4.java b/hapi-fhir-structures-r4/src/main/java/org/hl7/fhir/r4/hapi/fluentpath/FhirPathR4.java
index fe9732c5ad12..3570c2760a9d 100644
--- a/hapi-fhir-structures-r4/src/main/java/org/hl7/fhir/r4/hapi/fluentpath/FhirPathR4.java
+++ b/hapi-fhir-structures-r4/src/main/java/org/hl7/fhir/r4/hapi/fluentpath/FhirPathR4.java
@@ -19,8 +19,10 @@
 import org.hl7.fhir.r4.model.IdType;
 import org.hl7.fhir.r4.model.ValueSet;
 
+import java.util.Collections;
 import java.util.List;
 import java.util.Optional;
+import java.util.stream.Collectors;
 
 public class FhirPathR4 implements IFhirPath {
 
@@ -101,7 +103,10 @@ public List<Base> resolveConstant(
 					boolean beforeContext,
 					boolean explicitConstant)
 					throws PathEngineException {
-				return null;
+				return Collections.unmodifiableList(
+						theEvaluationContext.resolveConstant(appContext, name, beforeContext).stream()
+								.map(Base.class::cast)
+								.collect(Collectors.toList()));
 			}
 
 			@Override
diff --git a/hapi-fhir-validation/src/main/java/org/hl7/fhir/common/hapi/validation/validator/FhirInstanceValidator.java b/hapi-fhir-validation/src/main/java/org/hl7/fhir/common/hapi/validation/validator/FhirInstanceValidator.java
index e6cda6e082d0..95e98725e8d3 100644
--- a/hapi-fhir-validation/src/main/java/org/hl7/fhir/common/hapi/validation/validator/FhirInstanceValidator.java
+++ b/hapi-fhir-validation/src/main/java/org/hl7/fhir/common/hapi/validation/validator/FhirInstanceValidator.java
@@ -42,6 +42,7 @@ public class FhirInstanceValidator extends BaseValidatorBridge implements IInsta
 	private IValidatorResourceFetcher validatorResourceFetcher;
 	private IValidationPolicyAdvisor validatorPolicyAdvisor = new FhirDefaultPolicyAdvisor();
 	private boolean myAllowExamples;
+	private FHIRPathEngine.IEvaluationContext evaluationContext;
 
 	/**
 	 * Constructor
@@ -253,6 +254,7 @@ protected List<ValidationMessage> validate(IValidationContext<?> theValidationCt
 				.setValidatorResourceFetcher(getValidatorResourceFetcher())
 				.setAssumeValidRestReferences(isAssumeValidRestReferences())
 				.setAllowExamples(isAllowExamples())
+				.setEvaluationContext(getEvaluationContext())
 				.validate(wrappedWorkerContext, theValidationCtx);
 	}
 
@@ -296,6 +298,14 @@ public void setAssumeValidRestReferences(boolean assumeValidRestReferences) {
 		this.assumeValidRestReferences = assumeValidRestReferences;
 	}
 
+	public FHIRPathEngine.IEvaluationContext getEvaluationContext() {
+		return evaluationContext;
+	}
+
+	public void setEvaluationContext(FHIRPathEngine.IEvaluationContext evaluationContext) {
+		this.evaluationContext = evaluationContext;
+	}
+
 	/**
 	 * Clear any cached data held by the validator or any of its internal stores. This is mostly intended
 	 * for unit tests, but could be used for production uses too.
diff --git a/hapi-fhir-validation/src/main/java/org/hl7/fhir/common/hapi/validation/validator/ValidatorWrapper.java b/hapi-fhir-validation/src/main/java/org/hl7/fhir/common/hapi/validation/validator/ValidatorWrapper.java
index d1d198b4f0d8..43fc64abd7e0 100644
--- a/hapi-fhir-validation/src/main/java/org/hl7/fhir/common/hapi/validation/validator/ValidatorWrapper.java
+++ b/hapi-fhir-validation/src/main/java/org/hl7/fhir/common/hapi/validation/validator/ValidatorWrapper.java
@@ -55,6 +55,7 @@ class ValidatorWrapper {
 	private Collection<? extends String> myExtensionDomains;
 	private IValidatorResourceFetcher myValidatorResourceFetcher;
 	private IValidationPolicyAdvisor myValidationPolicyAdvisor;
+	private FHIRPathEngine.IEvaluationContext evaluationContext;
 	private boolean myAllowExamples;
 
 	/**
@@ -123,17 +124,14 @@ public ValidatorWrapper setValidatorResourceFetcher(IValidatorResourceFetcher va
 		return this;
 	}
 
+	public ValidatorWrapper setEvaluationContext(FHIRPathEngine.IEvaluationContext evaluationContext) {
+		this.evaluationContext = evaluationContext;
+		return this;
+	}
+
 	public List<ValidationMessage> validate(
 			IWorkerContext theWorkerContext, IValidationContext<?> theValidationContext) {
-		InstanceValidator v;
-		FHIRPathEngine.IEvaluationContext evaluationCtx = new FhirInstanceValidator.NullEvaluationContext();
-		XVerExtensionManager xverManager = new XVerExtensionManager(theWorkerContext);
-		try {
-			v = new InstanceValidator(
-					theWorkerContext, evaluationCtx, xverManager, new ValidatorSession(), new ValidatorSettings());
-		} catch (Exception e) {
-			throw new ConfigurationException(Msg.code(648) + e.getMessage(), e);
-		}
+		InstanceValidator v = getInstanceValidator(theWorkerContext);
 
 		v.setAssumeValidRestReferences(isAssumeValidRestReferences());
 		v.setBestPracticeWarningLevel(myBestPracticeWarningLevel);
@@ -235,6 +233,24 @@ public List<ValidationMessage> validate(
 		return messages;
 	}
 
+	private InstanceValidator getInstanceValidator(IWorkerContext theWorkerContext) {
+		InstanceValidator v;
+		FHIRPathEngine.IEvaluationContext evaluationCtx;
+		if (evaluationContext == null) {}
+		evaluationCtx = new FhirInstanceValidator.NullEvaluationContext();
+		if (evaluationContext != null) {
+			evaluationCtx = evaluationContext;
+		}
+		XVerExtensionManager xverManager = new XVerExtensionManager(theWorkerContext);
+		try {
+			v = new InstanceValidator(
+					theWorkerContext, evaluationCtx, xverManager, new ValidatorSession(), new ValidatorSettings());
+		} catch (Exception e) {
+			throw new ConfigurationException(Msg.code(648) + e.getMessage(), e);
+		}
+		return v;
+	}
+
 	private ReaderInputStream constructNewReaderInputStream(Reader theReader) {
 		try {
 			return ReaderInputStream.builder()