diff --git a/hapi-fhir-base/src/main/java/ca/uhn/fhir/validation/FhirValidator.java b/hapi-fhir-base/src/main/java/ca/uhn/fhir/validation/FhirValidator.java
index fde706d9f99..4d7b8ff161b 100644
--- a/hapi-fhir-base/src/main/java/ca/uhn/fhir/validation/FhirValidator.java
+++ b/hapi-fhir-base/src/main/java/ca/uhn/fhir/validation/FhirValidator.java
@@ -27,6 +27,7 @@ import ca.uhn.fhir.interceptor.api.Pointcut;
 import ca.uhn.fhir.rest.server.exceptions.InternalErrorException;
 import ca.uhn.fhir.util.BundleUtil;
 import ca.uhn.fhir.validation.schematron.SchematronProvider;
+import org.apache.commons.lang3.StringUtils;
 import org.apache.commons.lang3.Validate;
 import org.hl7.fhir.instance.model.api.IBase;
 import org.hl7.fhir.instance.model.api.IBaseBundle;
@@ -44,6 +45,8 @@ import java.util.function.Function;
 import java.util.stream.Collectors;
 import java.util.stream.IntStream;
 
+import static org.apache.commons.lang3.StringUtils.isBlank;
+
 
 /**
  * Resource validator, which checks resources for compliance against various validation schemes (schemas, schematrons, profiles, etc.)
@@ -277,24 +280,43 @@ public class FhirValidator {
 				return new ConcurrentValidationTask(entryPathPrefix, future);
 			}).collect(Collectors.toList());
 
-		List<SingleValidationMessage> validationMessages = new ArrayList<>();
+		List<SingleValidationMessage> validationMessages = buildValidationMessages(validationTasks);
+		return new ValidationResult(myContext, validationMessages);
+	}
+
+	static List<SingleValidationMessage> buildValidationMessages(List<ConcurrentValidationTask> validationTasks) {
+		List<SingleValidationMessage> retval = new ArrayList<>();
 		try {
 			for (ConcurrentValidationTask validationTask : validationTasks) {
 				ValidationResult result = validationTask.getFuture().get();
 				final String bundleEntryPathPrefix = validationTask.getResourcePathPrefix();
 				List<SingleValidationMessage> messages = result.getMessages().stream()
 					.map(message -> {
-						String currentPath = message.getLocationString().substring(message.getLocationString().indexOf('.'));
+						String currentPath;
+
+						String locationString = StringUtils.defaultIfEmpty(message.getLocationString(), "");
+
+						int dotIndex = locationString.indexOf('.');
+						if (dotIndex >= 0) {
+							currentPath = locationString.substring(dotIndex);
+						} else {
+							if (isBlank(bundleEntryPathPrefix) || isBlank(locationString)) {
+								currentPath = locationString;
+							} else {
+								currentPath = "." + locationString;
+							}
+						}
+
 						message.setLocationString(bundleEntryPathPrefix + currentPath);
 						return message;
 					})
 					.collect(Collectors.toList());
-				validationMessages.addAll(messages);
+				retval.addAll(messages);
 			}
 		} catch (InterruptedException | ExecutionException exp) {
 			throw new InternalErrorException(exp);
 		}
-		return new ValidationResult(myContext, new ArrayList<>(validationMessages));
+		return retval;
 	}
 
 	private ValidationResult validateResource(IValidationContext<IBaseResource> theValidationContext) {
@@ -353,11 +375,11 @@ public class FhirValidator {
 	}
 
 	// Simple Tuple to keep track of bundle path and associate aync future task
-	private static class ConcurrentValidationTask {
+	static class ConcurrentValidationTask {
 		private final String myResourcePathPrefix;
 		private final Future<ValidationResult> myFuture;
 
-		private ConcurrentValidationTask(String theResourcePathPrefix, Future<ValidationResult> theFuture) {
+		ConcurrentValidationTask(String theResourcePathPrefix, Future<ValidationResult> theFuture) {
 			myResourcePathPrefix = theResourcePathPrefix;
 			myFuture = theFuture;
 		}
diff --git a/hapi-fhir-base/src/test/java/ca/uhn/fhir/validation/FhirValidatorTest.java b/hapi-fhir-base/src/test/java/ca/uhn/fhir/validation/FhirValidatorTest.java
new file mode 100644
index 00000000000..5289e890eae
--- /dev/null
+++ b/hapi-fhir-base/src/test/java/ca/uhn/fhir/validation/FhirValidatorTest.java
@@ -0,0 +1,95 @@
+package ca.uhn.fhir.validation;
+
+import ca.uhn.fhir.context.FhirContext;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.Mock;
+import org.mockito.junit.jupiter.MockitoExtension;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.concurrent.CompletableFuture;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.hasSize;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+@ExtendWith(MockitoExtension.class)
+class FhirValidatorTest {
+	private static final String PREFIX = "Brakebills";
+	public static final String MESSAGE = "Fillory";
+	@Mock
+	FhirContext myFhirContext;
+
+	@Test
+	public void testBuildMessagesThreePartLocation() {
+		// setup
+		List<FhirValidator.ConcurrentValidationTask> tasks = buildTasks("patient.name.first");
+
+		// execute
+		List<SingleValidationMessage> resultMessages = FhirValidator.buildValidationMessages(tasks);
+
+		// validate
+		assertThat(resultMessages, hasSize(1));
+		assertEquals(MESSAGE, resultMessages.get(0).getMessage());
+		assertEquals(PREFIX + ".name.first", resultMessages.get(0).getLocationString());
+	}
+
+	@Test
+	public void testBuildMessagesTwoPartLocation() {
+		// setup
+		List<FhirValidator.ConcurrentValidationTask> tasks = buildTasks("patient.name");
+
+		// execute
+		List<SingleValidationMessage> resultMessages = FhirValidator.buildValidationMessages(tasks);
+
+		// validate
+		assertThat(resultMessages, hasSize(1));
+		assertEquals(MESSAGE, resultMessages.get(0).getMessage());
+		assertEquals(PREFIX + ".name", resultMessages.get(0).getLocationString());
+	}
+
+	@Test
+	public void testBuildMessagesNullLocation() {
+		// setup
+		List<FhirValidator.ConcurrentValidationTask> tasks = buildTasks(null);
+
+		// execute
+		List<SingleValidationMessage> resultMessages = FhirValidator.buildValidationMessages(tasks);
+
+		// validate
+		assertThat(resultMessages, hasSize(1));
+		assertEquals(MESSAGE, resultMessages.get(0).getMessage());
+		assertEquals(PREFIX, resultMessages.get(0).getLocationString());
+	}
+
+	@Test
+	public void testBuildMessagesOnePartLocation() {
+		// setup
+		List<FhirValidator.ConcurrentValidationTask> tasks = buildTasks("patient");
+
+		// execute
+		List<SingleValidationMessage> resultMessages = FhirValidator.buildValidationMessages(tasks);
+
+		// validate
+		assertThat(resultMessages, hasSize(1));
+		assertEquals(MESSAGE, resultMessages.get(0).getMessage());
+		assertEquals(PREFIX + ".patient", resultMessages.get(0).getLocationString());
+	}
+
+	private List<FhirValidator.ConcurrentValidationTask> buildTasks(String theLocation) {
+		SingleValidationMessage message = new SingleValidationMessage();
+		message.setMessage(MESSAGE);
+		message.setLocationString(theLocation);
+		ValidationResult result = new ValidationResult(myFhirContext, Collections.singletonList(message));
+		CompletableFuture<ValidationResult> future = new CompletableFuture<>();
+		future.complete(result);
+		List<FhirValidator.ConcurrentValidationTask> tasks = new ArrayList<>();
+		FhirValidator.ConcurrentValidationTask task = new FhirValidator.ConcurrentValidationTask(PREFIX, future);
+		tasks.add(task);
+		return tasks;
+	}
+
+
+}
diff --git a/hapi-fhir-docs/src/main/resources/ca/uhn/hapi/fhir/changelog/5_7_0/3266-concurrent-validation.yaml b/hapi-fhir-docs/src/main/resources/ca/uhn/hapi/fhir/changelog/5_7_0/3266-concurrent-validation.yaml
new file mode 100644
index 00000000000..f189fce21be
--- /dev/null
+++ b/hapi-fhir-docs/src/main/resources/ca/uhn/hapi/fhir/changelog/5_7_0/3266-concurrent-validation.yaml
@@ -0,0 +1,4 @@
+---
+type: fix
+issue: 3266
+title: "Concurrent validation failed with StringIndexOutOfBoundsException when the validation location did not contain a '.'. This has been corrected."