diff --git a/jme3-core/src/main/java/com/jme3/scene/UserData.java b/jme3-core/src/main/java/com/jme3/scene/UserData.java
index 2fb04f44d3..0d717abe7c 100644
--- a/jme3-core/src/main/java/com/jme3/scene/UserData.java
+++ b/jme3-core/src/main/java/com/jme3/scene/UserData.java
@@ -39,6 +39,7 @@
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.concurrent.atomic.AtomicLong;
 
 /**
  * <code>UserData</code> is used to contain user data objects
@@ -74,9 +75,15 @@ public final class UserData implements Savable {
     private static final int   TYPE_SHORT        = 10;
     private static final int   TYPE_BYTE         = 11;
 
+    private static final AtomicLong uniqueIdCounter = new AtomicLong(0);
+
+    private static final String LEGACY_PREFIX = "0";
+
     protected byte             type;
     protected Object           value;
 
+    private transient volatile String uniqueId;
+
     public UserData() {
     }
 
@@ -104,6 +111,17 @@ public String toString() {
         return value.toString();
     }
 
+  /**
+   * Prefix for list/map/array fields in the export capsule.
+   * Legacy files use "0" / "1"; new files use "udN_0" / "udN_1" (no ':' for XML).
+   */
+    private String listFieldPrefix(int index) {
+        if (LEGACY_PREFIX.equals(uniqueId)) {
+            return String.valueOf(index);
+        }
+        return uniqueId + "_" + index;
+    }
+
     public static byte getObjectType(Object type) {
         if (type instanceof Integer) {
             return TYPE_INTEGER;
@@ -138,7 +156,16 @@ public static byte getObjectType(Object type) {
     public void write(JmeExporter ex) throws IOException {
         OutputCapsule oc = ex.getCapsule(this);
         oc.write(type, "type", (byte) 0);
-        
+
+        if (uniqueId == null) {
+            synchronized (this) {
+                if (uniqueId == null) {
+                    uniqueId = "ud" + uniqueIdCounter.incrementAndGet();
+                }
+            }
+        }
+        oc.write(uniqueId, "uniqueId", null);
+
         switch (type) {
             case TYPE_INTEGER:
                 int i = (Integer) value;
@@ -165,15 +192,15 @@ public void write(JmeExporter ex) throws IOException {
                 oc.write(sav, "savableVal", null);
                 break;
             case TYPE_LIST:
-                this.writeList(oc, (List<?>) value, "0");
+                this.writeList(oc, (List<?>) value, listFieldPrefix(0));
                 break;
             case TYPE_MAP:
                 Map<?, ?> map = (Map<?, ?>) value;
-                this.writeList(oc, map.keySet(), "0");
-                this.writeList(oc, map.values(), "1");
+                this.writeList(oc, map.keySet(), listFieldPrefix(0));
+                this.writeList(oc, map.values(), listFieldPrefix(1));
                 break;
             case TYPE_ARRAY:
-                this.writeList(oc, Arrays.asList((Object[]) value), "0");
+                this.writeList(oc, Arrays.asList((Object[]) value), listFieldPrefix(0));
                 break;
             case TYPE_DOUBLE:
                 Double d = (Double) value;
@@ -196,6 +223,12 @@ public void write(JmeExporter ex) throws IOException {
     public void read(JmeImporter im) throws IOException {
         InputCapsule ic = im.getCapsule(this);
         type = ic.readByte("type", (byte) 0);
+
+        uniqueId = ic.readString("uniqueId", null);
+        if (uniqueId == null) {
+            uniqueId = LEGACY_PREFIX;
+        }
+
         switch (type) {
             case TYPE_INTEGER:
                 value = ic.readInt("intVal", 0);
@@ -216,19 +249,19 @@ public void read(JmeImporter im) throws IOException {
                 value = ic.readSavable("savableVal", null);
                 break;
             case TYPE_LIST:
-                value = this.readList(ic, "0");
+                value = this.readList(ic, listFieldPrefix(0));
                 break;
             case TYPE_MAP:
                 Map<Object, Object> map = new HashMap<>();
-                List<?> keys = this.readList(ic, "0");
-                List<?> values = this.readList(ic, "1");
+                List<?> keys = this.readList(ic, listFieldPrefix(0));
+                List<?> values = this.readList(ic, listFieldPrefix(1));
                 for (int i = 0; i < keys.size(); ++i) {
                     map.put(keys.get(i), values.get(i));
                 }
                 value = map;
                 break;
             case TYPE_ARRAY:
-                value = this.readList(ic, "0").toArray();
+                value = this.readList(ic, listFieldPrefix(0)).toArray();
                 break;
             case TYPE_DOUBLE:
                 value = ic.readDouble("doubleVal", 0.);
diff --git a/jme3-core/src/plugins/java/com/jme3/export/binary/BinaryInputCapsule.java b/jme3-core/src/plugins/java/com/jme3/export/binary/BinaryInputCapsule.java
index 989152d453..e0555442fd 100644
--- a/jme3-core/src/plugins/java/com/jme3/export/binary/BinaryInputCapsule.java
+++ b/jme3-core/src/plugins/java/com/jme3/export/binary/BinaryInputCapsule.java
@@ -959,6 +959,10 @@ protected long readLong(byte[] content) throws IOException {
         }
         bytes = ByteUtils.rightAlignBytes(bytes, 8);
         long value = ByteUtils.convertLongFromBytes(bytes);
+        if (value == BinaryOutputCapsule.NULL_OBJECT
+                || value == BinaryOutputCapsule.DEFAULT_OBJECT) {
+            index -= 4;
+        }
         return value;
     }
 
diff --git a/jme3-plugins/src/test/java/com/jme3/export/JmeExporterTest.java b/jme3-plugins/src/test/java/com/jme3/export/JmeExporterTest.java
index 96113bb6c9..e36490f950 100644
--- a/jme3-plugins/src/test/java/com/jme3/export/JmeExporterTest.java
+++ b/jme3-plugins/src/test/java/com/jme3/export/JmeExporterTest.java
@@ -140,7 +140,7 @@ public void testSaveWithNullParent(JmeExporter exporter) throws IOException {
     public void testExporterConsistency(JmeExporter currentExporter) {
         //
         final boolean testXML = true;
-        final boolean testLists = false;
+        final boolean testLists = true;
         final boolean testMaps = true;
         final boolean printXML = false;