diff --git a/core/src/main/java/org/incenp/obofoundry/kgcl/AutoIDAllocator.java b/core/src/main/java/org/incenp/obofoundry/kgcl/AutoIDAllocator.java
index af5d5d8..f7fd2d9 100644
--- a/core/src/main/java/org/incenp/obofoundry/kgcl/AutoIDAllocator.java
+++ b/core/src/main/java/org/incenp/obofoundry/kgcl/AutoIDAllocator.java
@@ -89,7 +89,9 @@ private boolean isAuto(String id) {
     private String getAutoID(String id) {
         String autoID = idMap.get(id);
         if ( autoID == null ) {
-            autoID = idGenerator.nextID();
+            if ( idGenerator != null ) {
+                autoID = idGenerator.nextID();
+            }
             if ( autoID == null ) {
                 unallocatedIDs.add(id);
                 autoID = id;