diff --git a/user-manager-server/src/main/java/de/ozgcloud/user/UserResourceMapper.java b/user-manager-server/src/main/java/de/ozgcloud/user/UserResourceMapper.java
index f9f2486ea48654c5493876af69f760f9b1367daf..6dfc125640d0f379e2153d96f9c07ed511e7278b 100644
--- a/user-manager-server/src/main/java/de/ozgcloud/user/UserResourceMapper.java
+++ b/user-manager-server/src/main/java/de/ozgcloud/user/UserResourceMapper.java
@@ -93,6 +93,7 @@ public abstract class UserResourceMapper {
 				.map(this::mapGroup)
 				.filter(Objects::nonNull)
 				.map(attributeMap -> attributeMap.get(properties.organisationsEinheitIdKey()))
+				.filter(Objects::nonNull)
 				.flatMap(Collection::stream);
 	}
 
diff --git a/user-manager-server/src/test/java/de/ozgcloud/user/GroupRepresentationTestFactory.java b/user-manager-server/src/test/java/de/ozgcloud/user/GroupRepresentationTestFactory.java
index ef6f392a0ca35993bd50422df19a42ac3a69367b..8be817f43c5f957db4e55ba5c1959b42ff75a07b 100644
--- a/user-manager-server/src/test/java/de/ozgcloud/user/GroupRepresentationTestFactory.java
+++ b/user-manager-server/src/test/java/de/ozgcloud/user/GroupRepresentationTestFactory.java
@@ -36,11 +36,15 @@ class GroupRepresentationTestFactory {
 	}
 
 	public static GroupRepresentation createByPathAndOrganisationEinheitIds(String groupPath, String... organisationEinheitIds) {
+		return createWithPathAndAttributes(groupPath, Map.of(UserResourceMapperTest.ORGANISATIONS_EINHEIT_ID_KEY,
+				List.of(organisationEinheitIds)));
+	}
+
+	public static GroupRepresentation createWithPathAndAttributes(String groupPath, Map<String, List<String>> attributes) {
 		var groupRepresentation = new GroupRepresentation();
 		groupRepresentation.setName(groupPath);
 		groupRepresentation.setPath(groupPath);
-		groupRepresentation.setAttributes(Map.of(UserResourceMapperTest.ORGANISATIONS_EINHEIT_ID_KEY,
-				List.of(organisationEinheitIds)));
+		groupRepresentation.setAttributes(attributes);
 		return groupRepresentation;
 	}
 }
diff --git a/user-manager-server/src/test/java/de/ozgcloud/user/UserResourceMapperTest.java b/user-manager-server/src/test/java/de/ozgcloud/user/UserResourceMapperTest.java
index effcd75641189d1acd52922498cabd394175d55f..beb45ba1b47c07cd6933a005b8bb07f446d0c624 100644
--- a/user-manager-server/src/test/java/de/ozgcloud/user/UserResourceMapperTest.java
+++ b/user-manager-server/src/test/java/de/ozgcloud/user/UserResourceMapperTest.java
@@ -56,6 +56,7 @@ class UserResourceMapperTest {
 	static final String ORGANISATIONS_EINHEIT_ID_2 = "4711";
 	static final String GROUP_1_PATH = "/group1";
 	static final String GROUP_2_PATH = "/group2";
+	static final String GROUP_3_PATH = "/group3";
 
 	@Spy
 	@InjectMocks
@@ -186,12 +187,25 @@ class UserResourceMapperTest {
 				GROUP_1_PATH, ORGANISATIONS_EINHEIT_ID_1, ORGANISATIONS_EINHEIT_ID_3);
 		private final GroupRepresentation group2 = GroupRepresentationTestFactory.createByPathAndOrganisationEinheitIds(
 				GROUP_2_PATH, ORGANISATIONS_EINHEIT_ID_2);
+		private final GroupRepresentation group3 = GroupRepresentationTestFactory.createWithPathAndAttributes(
+				GROUP_3_PATH, Map.of());
 
 		@BeforeEach
 		void beforeEach() {
 			when(properties.organisationsEinheitIdKey()).thenReturn(ORGANISATIONS_EINHEIT_ID_KEY);
 		}
 
+		@DisplayName("should map no organisations einheit id if group has none")
+		@Test
+		void shouldMapNoOrganisationsEinheitIdIfGroupHasNone() {
+			when(realm.getGroupByPath(GROUP_3_PATH)).thenReturn(group3);
+			var userResource = UserResourceTestFactory.createWithGroups(group3);
+
+			var result = mapper.mapOrganisationsEinheitIds(userResource);
+
+			assertThat(result).isEmpty();
+		}
+
 		@Test
 		void shouldMapOrganisationsEinheitIdsFromSingleGroup() {
 			var userResource = UserResourceTestFactory.createWithGroups(group1);
@@ -204,9 +218,10 @@ class UserResourceMapperTest {
 
 		@Test
 		void shouldMapOrganisationsEinheitIdsFromGroups() {
-			var userResource = UserResourceTestFactory.createWithGroups(group1, group2);
+			var userResource = UserResourceTestFactory.createWithGroups(group1, group2, group3);
 			when(realm.getGroupByPath(GROUP_1_PATH)).thenReturn(group1);
 			when(realm.getGroupByPath(GROUP_2_PATH)).thenReturn(group2);
+			when(realm.getGroupByPath(GROUP_3_PATH)).thenReturn(group3);
 
 			var result = mapper.mapOrganisationsEinheitIds(userResource);