diff --git a/spring-data-neo4j/src/main/java/org/springframework/data/neo4j/repository/support/SimpleNeo4jRepository.java b/spring-data-neo4j/src/main/java/org/springframework/data/neo4j/repository/support/SimpleNeo4jRepository.java
index fa4affefe..e8980aa2e 100644
--- a/spring-data-neo4j/src/main/java/org/springframework/data/neo4j/repository/support/SimpleNeo4jRepository.java
+++ b/spring-data-neo4j/src/main/java/org/springframework/data/neo4j/repository/support/SimpleNeo4jRepository.java
@@ -43,6 +43,7 @@ import org.springframework.util.Assert;
  * @author Mark Paluch
  * @author Jens Schauder
  * @author Gerrit Meier
+ * @author Michael J. Simons
  */
 @Repository
 @Transactional(readOnly = true)
@@ -140,6 +141,7 @@ public class SimpleNeo4jRepository<T, ID extends Serializable> implements Neo4jR
 
 	@Override
 	public Optional<T> findById(ID id, int depth) {
+		Assert.notNull(id, ID_MUST_NOT_BE_NULL);
 		return Optional.ofNullable(session.load(clazz, id, depth));
 	}
 
diff --git a/spring-data-neo4j/src/test/java/org/springframework/data/neo4j/repository/support/SimpleNeo4jRepositoryTests.java b/spring-data-neo4j/src/test/java/org/springframework/data/neo4j/repository/support/SimpleNeo4jRepositoryTests.java
index bb7b7d8df..53658f5a5 100644
--- a/spring-data-neo4j/src/test/java/org/springframework/data/neo4j/repository/support/SimpleNeo4jRepositoryTests.java
+++ b/spring-data-neo4j/src/test/java/org/springframework/data/neo4j/repository/support/SimpleNeo4jRepositoryTests.java
@@ -28,6 +28,10 @@ import org.neo4j.ogm.session.Session;
 import org.springframework.data.domain.Page;
 import org.springframework.data.domain.PageRequest;
 
+/**
+ * @author Gerrit Meier
+ * @author Michael J. Simons
+ */
 public class SimpleNeo4jRepositoryTests {
 
 	private final Session sessionMock = mock(Session.class);
@@ -136,6 +140,22 @@ public class SimpleNeo4jRepositoryTests {
 		assertThat(page.getTotalElements()).isEqualTo(amountOfElementsInDatabase);
 	}
 
+	@Test // DATAGRAPH-1260
+	public void idShouldBeAsserted() {
+
+		assertThatIllegalArgumentException()
+				.isThrownBy(() -> repository.findById(null))
+				.withMessage("The given id must not be null!");
+	}
+
+	@Test // DATAGRAPH-1260
+	public void idShouldBeAssertedWithDepth() {
+
+		assertThatIllegalArgumentException()
+				.isThrownBy(() -> repository.findById(null, 42))
+				.withMessage("The given id must not be null!");
+	}
+
 	private Page loadPage(PageRequest requestedPage, long amountOfElementsInDatabase) {
 		prepareSessionMock(requestedPage, amountOfElementsInDatabase);
 		return repository.findAll(requestedPage);