diff --git a/commons/src/main/java/org/archive/util/ObjectIdentityBdbCache.java b/commons/src/main/java/org/archive/util/ObjectIdentityBdbCache.java
index f324d946..995715d7 100644
--- a/commons/src/main/java/org/archive/util/ObjectIdentityBdbCache.java
+++ b/commons/src/main/java/org/archive/util/ObjectIdentityBdbCache.java
@@ -331,6 +331,9 @@ implements ObjectIdentityCache<String, V>, Closeable, Serializable {
      * @see org.archive.util.ObjectIdentityCache#size()
      */
     public int size() {
+        if(db==null) {
+            return 0; 
+        }
         return diskMap.size();
     }