diff --git a/src/main/java/org/olat/modules/lecture/manager/LectureServiceImpl.java b/src/main/java/org/olat/modules/lecture/manager/LectureServiceImpl.java
index 34b0b26c136f174e692860cc70c88c7a08dc07b8..c6aeb2f39bf8efeb653cdf377c7f898a251463ea 100644
--- a/src/main/java/org/olat/modules/lecture/manager/LectureServiceImpl.java
+++ b/src/main/java/org/olat/modules/lecture/manager/LectureServiceImpl.java
@@ -859,6 +859,7 @@ public class LectureServiceImpl implements LectureService, UserDataDeletable, De
 	
 	@Override
 	public List<TaxonomyLevel> getTaxonomy(LectureBlockRef lectureBlock) {
+		if(lectureBlock == null || lectureBlock.getKey() == null) return Collections.emptyList();
 		return lectureBlockToTaxonomyLevelDao.getTaxonomyLevels(lectureBlock);
 	}