diff --git a/Changes b/Changes
index 3c37bd3..9bdcd93 100644
--- a/Changes
+++ b/Changes
@@ -1,6 +1,7 @@
-0.39 2022-11-16
+0.39 2023-01-12
     - Updated to Java 11
     - Dependencies updated
+    - Fix reference bug in Annis (resolved #129, diewald)
 
 0.38.2 2022-10-05
     - [feature] Improve regex treatment of negative
diff --git a/src/main/java/de/ids_mannheim/korap/query/serialize/AnnisQueryProcessor.java b/src/main/java/de/ids_mannheim/korap/query/serialize/AnnisQueryProcessor.java
index 661a331..9d2ecb7 100644
--- a/src/main/java/de/ids_mannheim/korap/query/serialize/AnnisQueryProcessor.java
+++ b/src/main/java/de/ids_mannheim/korap/query/serialize/AnnisQueryProcessor.java
@@ -718,7 +718,8 @@
                     group = KoralObjectGenerator
                             .makeGroup(KoralOperation.RELATION);
                     Map<String, Object> relation = new HashMap<String, Object>();
-                    putAllBut(relation, operatorGroup, "groupType");
+                    if (operatorGroup != null)
+                        putAllBut(relation, operatorGroup, "groupType");
                     group.put("relType", relation);
                 }
                 else if (groupType.equals("sequence")) {
@@ -1347,4 +1348,5 @@
         }
         return tree;
     }
-}
\ No newline at end of file
+}
+
diff --git a/src/test/java/de/ids_mannheim/korap/query/test/annis/AnnisQueryProcessorTest.java b/src/test/java/de/ids_mannheim/korap/query/test/annis/AnnisQueryProcessorTest.java
index 12da8b6..cd6baa9 100644
--- a/src/test/java/de/ids_mannheim/korap/query/test/annis/AnnisQueryProcessorTest.java
+++ b/src/test/java/de/ids_mannheim/korap/query/test/annis/AnnisQueryProcessorTest.java
@@ -1176,4 +1176,14 @@
     }
      */
 
+    @Test
+    public void testReferenceBug () throws Exception {
+        query = "tok & tok & #1 .1,11 #2 & #1 == #2";
+        qs.setQuery(query, "annis");
+        res = mapper.readTree(qs.toJSON());
+
+        // Not sure the serialization is correct, but it no longer throws a null pointer exception
+        assertEquals("koral:reference", res.at("/query/operands/1/@type").asText());
+        assertEquals("operation:relation", res.at("/query/operation").asText());
+    }
 }