diff --git a/src/osgDB/FieldReaderIterator.cpp b/src/osgDB/FieldReaderIterator.cpp
index 1fada854d..5622501f6 100644
--- a/src/osgDB/FieldReaderIterator.cpp
+++ b/src/osgDB/FieldReaderIterator.cpp
@@ -80,6 +80,10 @@ void FieldReaderIterator::_copy(const FieldReaderIterator& ic)
     {
         _previousField = new Field(*ic._previousField);
     }
+    else
+    {
+        _previousField = NULL;
+    }
 
     if (ic._fieldQueue && ic._fieldQueueCapacity>0)
     {