diff --git a/jbrowse/src/org/labkey/jbrowse/JBrowseFieldUtils.java b/jbrowse/src/org/labkey/jbrowse/JBrowseFieldUtils.java
index c4a31e3c5..22dee6a04 100644
--- a/jbrowse/src/org/labkey/jbrowse/JBrowseFieldUtils.java
+++ b/jbrowse/src/org/labkey/jbrowse/JBrowseFieldUtils.java
@@ -101,7 +101,7 @@ public static Map<String, JBrowseFieldDescriptor> getIndexedFields(JsonFile json
     }
 
     public static Map<String, JBrowseFieldDescriptor> getGenotypeDependentFields(@Nullable JsonFile jsonFile) {
-        String key = "genotypeFields." + jsonFile.getObjectId();
+        String key = "genotypeFields." + (jsonFile == null ? "default" : jsonFile.getObjectId());
         if (_cache.get(key) == null)
         {
             Map<String, JBrowseFieldDescriptor> ret = new HashMap<>();