diff --git a/src/main/java/org/springframework/data/repository/support/DomainClassConverter.java b/src/main/java/org/springframework/data/repository/support/DomainClassConverter.java
index 828c5ff3a..d7fa74985 100644
--- a/src/main/java/org/springframework/data/repository/support/DomainClassConverter.java
+++ b/src/main/java/org/springframework/data/repository/support/DomainClassConverter.java
@@ -82,7 +82,7 @@ public class DomainClassConverter<T extends ConversionService & ConverterRegistr
 	@Nullable
 	@Override
 	public Object convert(@Nullable Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {
-		return getConverter(targetType).map(it -> it.convert(source, sourceType, targetType)).orElse(source);
+		return getConverter(targetType).map(it -> it.convert(source, sourceType, targetType)).orElse(null);
 	}
 
 	/*
diff --git a/src/test/java/org/springframework/data/repository/support/DomainClassConverterUnitTests.java b/src/test/java/org/springframework/data/repository/support/DomainClassConverterUnitTests.java
index 29ae01b8c..a2bb29c04 100755
--- a/src/test/java/org/springframework/data/repository/support/DomainClassConverterUnitTests.java
+++ b/src/test/java/org/springframework/data/repository/support/DomainClassConverterUnitTests.java
@@ -30,6 +30,7 @@ import org.mockito.junit.jupiter.MockitoExtension;
 import org.mockito.junit.jupiter.MockitoSettings;
 import org.mockito.quality.Strictness;
 import org.springframework.aop.framework.Advised;
+import org.springframework.aop.framework.AopProxyUtils;
 import org.springframework.beans.factory.support.BeanDefinitionBuilder;
 import org.springframework.beans.factory.support.DefaultListableBeanFactory;
 import org.springframework.context.ApplicationContext;
@@ -203,6 +204,23 @@ class DomainClassConverterUnitTests {
 		assertThat(conversionService.canConvert(String.class, User.class)).isTrue();
 	}
 
+	@Test // DATACMNS-1743
+	void returnsNullForFailedLookup() {
+
+		ApplicationContext context = initContextWithRepo();
+		converter.setApplicationContext(context);
+
+		// Expect ID conversion
+		doReturn(4711L).when(service).convert("4711", Long.class);
+
+		// Configure aggregate lookup to fail
+		UserRepository users = context.getBean(UserRepository.class);
+		users = (UserRepository) AopProxyUtils.getSingletonTarget(users);
+		doReturn(Optional.empty()).when(users).findById(any());
+
+		assertThat(converter.convert("4711", STRING_TYPE, USER_TYPE)).isNull();
+	}
+
 	private ApplicationContext initContextWithRepo() {
 
 		BeanDefinitionBuilder builder = BeanDefinitionBuilder.rootBeanDefinition(DummyRepositoryFactoryBean.class);