diff --git a/hapi-fhir-docs/src/main/resources/ca/uhn/hapi/fhir/changelog/7_4_0/5957-fix-mdm-class-cast-exception-when-phonetically-matching-by-humanname.yaml b/hapi-fhir-docs/src/main/resources/ca/uhn/hapi/fhir/changelog/7_4_0/5957-fix-mdm-class-cast-exception-when-phonetically-matching-by-humanname.yaml
new file mode 100644
index 00000000000..e36aad6dae1
--- /dev/null
+++ b/hapi-fhir-docs/src/main/resources/ca/uhn/hapi/fhir/changelog/7_4_0/5957-fix-mdm-class-cast-exception-when-phonetically-matching-by-humanname.yaml
@@ -0,0 +1,5 @@
+---
+type: fix
+issue: 6077
+title: "Previously, when a MDM rule tried to perform a phonetic match by HumanName (eg. Patient.name), a 
+`ClassCastException` was thrown. This has now been fixed."
diff --git a/hapi-fhir-server-mdm/src/main/java/ca/uhn/fhir/mdm/rules/matcher/fieldmatchers/PhoneticEncoderMatcher.java b/hapi-fhir-server-mdm/src/main/java/ca/uhn/fhir/mdm/rules/matcher/fieldmatchers/PhoneticEncoderMatcher.java
index 26e91559811..7c31fbd3314 100644
--- a/hapi-fhir-server-mdm/src/main/java/ca/uhn/fhir/mdm/rules/matcher/fieldmatchers/PhoneticEncoderMatcher.java
+++ b/hapi-fhir-server-mdm/src/main/java/ca/uhn/fhir/mdm/rules/matcher/fieldmatchers/PhoneticEncoderMatcher.java
@@ -45,9 +45,17 @@ public class PhoneticEncoderMatcher implements IMdmFieldMatcher {
 
 	@Override
 	public boolean matches(IBase theLeftBase, IBase theRightBase, MdmMatcherJson theParams) {
-		String leftString = StringMatcherUtils.extractString((IPrimitiveType<?>) theLeftBase, theParams.getExact());
-		String rightString = StringMatcherUtils.extractString((IPrimitiveType<?>) theRightBase, theParams.getExact());
+		if (theLeftBase instanceof IPrimitiveType && theRightBase instanceof IPrimitiveType) {
+			String leftString = StringMatcherUtils.extractString((IPrimitiveType<?>) theLeftBase, theParams.getExact());
+			String rightString =
+					StringMatcherUtils.extractString((IPrimitiveType<?>) theRightBase, theParams.getExact());
 
-		return matches(leftString, rightString);
+			return matches(leftString, rightString);
+		}
+		ourLog.warn(
+				"Unable to evaluate match between {} and {} because they are not an instance of PrimitiveType.",
+				theLeftBase.getClass().getSimpleName(),
+				theRightBase.getClass().getSimpleName());
+		return false;
 	}
 }
diff --git a/hapi-fhir-server-mdm/src/test/java/ca/uhn/fhir/mdm/rules/svc/ResourceMatcherR4Test.java b/hapi-fhir-server-mdm/src/test/java/ca/uhn/fhir/mdm/rules/svc/ResourceMatcherR4Test.java
index 8fa816bc5f1..74ab179211d 100644
--- a/hapi-fhir-server-mdm/src/test/java/ca/uhn/fhir/mdm/rules/svc/ResourceMatcherR4Test.java
+++ b/hapi-fhir-server-mdm/src/test/java/ca/uhn/fhir/mdm/rules/svc/ResourceMatcherR4Test.java
@@ -6,15 +6,29 @@ import ca.uhn.fhir.mdm.api.MdmMatchResultEnum;
 import ca.uhn.fhir.mdm.rules.json.MdmFieldMatchJson;
 import ca.uhn.fhir.mdm.rules.json.MdmMatcherJson;
 import ca.uhn.fhir.mdm.rules.json.MdmRulesJson;
+import ca.uhn.fhir.mdm.rules.matcher.fieldmatchers.PhoneticEncoderMatcher;
 import ca.uhn.fhir.mdm.rules.matcher.models.MatchTypeEnum;
+import ch.qos.logback.classic.Level;
+import ch.qos.logback.classic.Logger;
+import ch.qos.logback.classic.spi.ILoggingEvent;
+import ch.qos.logback.core.Appender;
 import org.hl7.fhir.r4.model.HumanName;
 import org.hl7.fhir.r4.model.Patient;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
+import org.mockito.ArgumentCaptor;
+import org.mockito.Captor;
+import org.mockito.Mock;
+import org.slf4j.LoggerFactory;
 
 import java.util.Arrays;
+import java.util.List;
 
+import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.verifyNoMoreInteractions;
 import static org.mockito.Mockito.when;
 
 public class ResourceMatcherR4Test extends BaseMdmRulesR4Test {
@@ -23,6 +37,10 @@ public class ResourceMatcherR4Test extends BaseMdmRulesR4Test {
 	public static final String PHONE_NUMBER = "123 456789";
 	private Patient myLeft;
 	private Patient myRight;
+	@Mock
+	private Appender<ILoggingEvent> myAppender;
+	@Captor
+	ArgumentCaptor<ILoggingEvent> myLoggingEvent;
 
 	@Override
 	@BeforeEach
@@ -61,6 +79,41 @@ public class ResourceMatcherR4Test extends BaseMdmRulesR4Test {
 		assertMatchResult(MdmMatchResultEnum.MATCH, 7L, 3.0, false, false, result);
 	}
 
+	@Test
+	public void testMetaphoneOnName() {
+		Logger logger = (Logger) LoggerFactory.getLogger(PhoneticEncoderMatcher.class);
+		logger.addAppender(myAppender);
+
+		// Given: MDM rules that match by Patient.name using some phonetic algorithm
+		MdmFieldMatchJson lastNameMatchField = new MdmFieldMatchJson()
+			.setName(PATIENT_FAMILY)
+			.setResourceType("Patient")
+			.setResourcePath("name")
+			.setMatcher(new MdmMatcherJson().setAlgorithm(MatchTypeEnum.METAPHONE));
+
+		MdmRulesJson retval = new MdmRulesJson();
+		retval.setVersion("test version");
+		retval.addMatchField(lastNameMatchField);
+		retval.setMdmTypes(List.of("Patient"));
+		retval.putMatchResult(PATIENT_FAMILY, MdmMatchResultEnum.MATCH);
+
+		// When
+		MdmResourceMatcherSvc matcherSvc = buildMatcher(retval);
+		MdmMatchOutcome result = matcherSvc.match(myLeft, myRight);
+
+		// Then: expect a logged message notifying that we are unable to phonetically match by HumanName
+		verify(myAppender, times(1)).doAppend(myLoggingEvent.capture());
+		ILoggingEvent event = myLoggingEvent.getValue();
+		assertEquals(Level.WARN, event.getLevel());
+		assertEquals("Unable to evaluate match between HumanName and HumanName because they are not an instance of PrimitiveType.", event.getFormattedMessage());
+
+		logger.detachAppender(myAppender);
+		verifyNoMoreInteractions(myAppender);
+		System.clearProperty("unit_test");
+
+		assertMatchResult(MdmMatchResultEnum.NO_MATCH, 0L, 0.0, false, false, result);
+	}
+
 	@Test
 	public void testStringMatchResult() {
 		MdmResourceMatcherSvc matcherSvc = buildMatcher(buildNamePhoneRules(MatchTypeEnum.STRING));