diff --git a/src/caosdb/utils/plantuml.py b/src/caosdb/utils/plantuml.py
index 31b562f983d5a189a352ac33758182269dc6dc40..795c0409bbeaad7a52376bebc7807103c07dd2b2 100644
--- a/src/caosdb/utils/plantuml.py
+++ b/src/caosdb/utils/plantuml.py
@@ -36,6 +36,7 @@ plantuml FILENAME.pu -> FILENAME.png
 import os
 
 import caosdb as db
+from caosdb.common.datatype import is_reference, get_referenced_recordtype
 
 REFERENCE = "REFERENCE"