diff --git a/src/main/java/ch/ethz/seb/sebserver/gbl/model/EntityName.java b/src/main/java/ch/ethz/seb/sebserver/gbl/model/EntityName.java
index dc8eea7f..a27b37f4 100644
--- a/src/main/java/ch/ethz/seb/sebserver/gbl/model/EntityName.java
+++ b/src/main/java/ch/ethz/seb/sebserver/gbl/model/EntityName.java
@@ -30,7 +30,7 @@ public class EntityName extends EntityKey {
     public EntityName(
             @JsonProperty(value = API.PARAM_MODEL_ID, required = true) final String id,
             @JsonProperty(value = API.PARAM_ENTITY_TYPE, required = true) final EntityType entityType,
-            @JsonProperty(value = ATTR_NAME, required = true) final String name) {
+            @JsonProperty(value = ATTR_NAME) final String name) {
 
         super(id, entityType);
         this.name = name;
diff --git a/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/impl/UserActivityLogDAOImpl.java b/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/impl/UserActivityLogDAOImpl.java
index 6f8df72e..461b4f2f 100644
--- a/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/impl/UserActivityLogDAOImpl.java
+++ b/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/impl/UserActivityLogDAOImpl.java
@@ -465,7 +465,9 @@ public class UserActivityLogDAOImpl implements UserActivityLogDAO {
                 .map(record -> new UserActivityLog(
                         record.getId(),
                         record.getUserUuid(),
-                        userMapping.get(record.getUserUuid()),
+                        (userMapping.containsKey(record.getUserUuid()))
+                                ? userMapping.get(record.getUserUuid())
+                                : "--",
                         record.getTimestamp(),
                         UserLogActivityType.valueOf(record.getActivityType()),
                         EntityType.valueOf(record.getEntityType()),
diff --git a/src/test/java/ch/ethz/seb/sebserver/gui/integration/UseCasesIntegrationTest.java b/src/test/java/ch/ethz/seb/sebserver/gui/integration/UseCasesIntegrationTest.java
index 38e2ffc4..5eea7de8 100644
--- a/src/test/java/ch/ethz/seb/sebserver/gui/integration/UseCasesIntegrationTest.java
+++ b/src/test/java/ch/ethz/seb/sebserver/gui/integration/UseCasesIntegrationTest.java
@@ -27,7 +27,7 @@ import java.util.stream.Collectors;
 import org.apache.commons.codec.Charsets;
 import org.apache.commons.io.IOUtils;
 import org.apache.commons.lang3.BooleanUtils;
-import org.apache.tomcat.util.buf.StringUtils;
+import org.apache.commons.lang3.StringUtils;
 import org.joda.time.DateTimeZone;
 import org.junit.After;
 import org.junit.Before;
@@ -122,7 +122,10 @@ import ch.ethz.seb.sebserver.gui.service.remote.webservice.api.lmssetup.GetLmsSe
 import ch.ethz.seb.sebserver.gui.service.remote.webservice.api.lmssetup.NewLmsSetup;
 import ch.ethz.seb.sebserver.gui.service.remote.webservice.api.lmssetup.SaveLmsSetup;
 import ch.ethz.seb.sebserver.gui.service.remote.webservice.api.lmssetup.TestLmsSetup;
+import ch.ethz.seb.sebserver.gui.service.remote.webservice.api.logs.DeleteAllUserLogs;
 import ch.ethz.seb.sebserver.gui.service.remote.webservice.api.logs.GetExtendedClientEventPage;
+import ch.ethz.seb.sebserver.gui.service.remote.webservice.api.logs.GetUserLogNames;
+import ch.ethz.seb.sebserver.gui.service.remote.webservice.api.logs.GetUserLogPage;
 import ch.ethz.seb.sebserver.gui.service.remote.webservice.api.quiz.GetQuizData;
 import ch.ethz.seb.sebserver.gui.service.remote.webservice.api.quiz.GetQuizPage;
 import ch.ethz.seb.sebserver.gui.service.remote.webservice.api.quiz.ImportAsExam;
@@ -2494,4 +2497,52 @@ public class UseCasesIntegrationTest extends GuiIntegrationTest {
         }
     }
 
+    @Test
+    @Order(20)
+    // *************************************
+    // Use Case 20: Login as admin and get and delete user activity logs
+    public void testUsecase20_DeleteUserActivityLogs() throws IOException {
+        final RestServiceImpl restService = createRestServiceForUser(
+                "admin",
+                "admin",
+                new GetUserLogPage(),
+                new GetUserLogNames(),
+                new DeleteAllUserLogs());
+
+        // get all user logs
+        final List<EntityName> allUserLogs = restService.getBuilder(GetUserLogNames.class)
+                .call()
+                .getOrThrow();
+
+        assertNotNull(allUserLogs);
+        assertFalse(allUserLogs.isEmpty());
+
+        // delete unknown user logs
+        final String toDelete = StringUtils.join(allUserLogs.stream()
+                .filter(log -> log.name.equals("--"))
+                .map(name -> name.getModelId())
+                .collect(Collectors.toList()), ",");
+
+        final EntityProcessingReport report = restService.getBuilder(DeleteAllUserLogs.class)
+                .withFormParam(API.PARAM_MODEL_ID_LIST, toDelete)
+                .call()
+                .getOrThrow();
+
+        assertNotNull(report);
+        assertTrue(report.errors.isEmpty());
+        assertFalse(report.results.isEmpty());
+
+        final List<EntityName> allUserLogsAfterDel = restService.getBuilder(GetUserLogNames.class)
+                .call()
+                .getOrThrow();
+
+        assertNotNull(allUserLogsAfterDel);
+        assertFalse(allUserLogsAfterDel.isEmpty());
+        assertTrue(allUserLogsAfterDel.stream()
+                .filter(log -> log.name.equals("--"))
+                .map(name -> name.getModelId())
+                .collect(Collectors.toList()).isEmpty());
+
+    }
+
 }