diff --git a/include/osgDB/StreamOperator b/include/osgDB/StreamOperator
index f808d2d7d..2813f017c 100644
--- a/include/osgDB/StreamOperator
+++ b/include/osgDB/StreamOperator
@@ -8,6 +8,9 @@
 namespace osgDB
 {
 
+// forward declare
+class InputStream;
+
 class OSGDB_EXPORT OutputIterator : public osg::Referenced
 {
 public:
@@ -64,12 +67,16 @@ protected:
 class OSGDB_EXPORT InputIterator : public osg::Referenced
 {
 public:
-    InputIterator() : _in(0), _failed(false) {}
+    InputIterator() : _in(0), _inputStream(0), _failed(false) {}
     virtual ~InputIterator() {}
     
     void setStream( std::istream* istream ) { _in = istream; }
     std::istream* getStream() { return _in; }
     const std::istream* getStream() const { return _in; }
+
+    void setInputStream( InputStream* inputStream) { _inputStream = inputStream; }
+    InputStream* getInputStream() { return _inputStream; }
+    const InputStream* getInputStream() const { return _inputStream; }
     
     void checkStream() const { if (_in->rdstate()&_in->failbit) _failed = true; }
     bool isFailed() const { return _failed; }
@@ -100,9 +107,12 @@ public:
     
     virtual bool matchString( const std::string& /*str*/ ) { return false; }
     virtual void advanceToCurrentEndBracket() {}
-    
+
+    void throwException( const std::string& msg );
+
 protected:
-    std::istream* _in;
+    std::istream*       _in;
+    osgDB::InputStream* _inputStream;
     mutable bool _failed;
 };
 
diff --git a/src/osgDB/InputStream.cpp b/src/osgDB/InputStream.cpp
index b24917b0e..a86820bfe 100644
--- a/src/osgDB/InputStream.cpp
+++ b/src/osgDB/InputStream.cpp
@@ -692,6 +692,8 @@ InputStream::ReadType InputStream::start( InputIterator* inIterator )
     if ( !_in )
         throwException( "InputStream: Null stream specified." );
     if ( getException() ) return type;
+
+    _in->setInputStream(this);
     
     // Check OSG header information
     unsigned int version = 0;
diff --git a/src/osgPlugins/osg/BinaryStreamOperator.h b/src/osgPlugins/osg/BinaryStreamOperator.h
index 77541444d..b8f140141 100644
--- a/src/osgPlugins/osg/BinaryStreamOperator.h
+++ b/src/osgPlugins/osg/BinaryStreamOperator.h
@@ -145,11 +145,15 @@ public:
     virtual void readString( std::string& s )
     {
         int size = 0; readInt( size );
-        if ( size )
+        if ( size>0 )
         {
             s.resize( size );
             _in->read( (char*)s.c_str(), size );
         }
+        else if ( size<0 ) 
+        {
+            throwException( "InputStream::readString() error, negative string size read." );
+        }
     }
     
     virtual void readStream( std::istream& (*fn)(std::istream&) ) {}