diff --git a/include/wx/mstream.h b/include/wx/mstream.h
index 0f73867261..3bd53e642d 100644
--- a/include/wx/mstream.h
+++ b/include/wx/mstream.h
@@ -14,9 +14,13 @@
 #include <wx/stream.h>
 
 class wxMemoryInputStream: public wxInputStream {
+ private:
+  size_t m_length;
+  
  public:
   wxMemoryInputStream(const char *data, size_t length);
   virtual ~wxMemoryInputStream();
+  virtual size_t StreamSize() const { return m_length; }
 
   char Peek();
 };
diff --git a/src/common/mstream.cpp b/src/common/mstream.cpp
index 35e384bade..560c0fd1ae 100644
--- a/src/common/mstream.cpp
+++ b/src/common/mstream.cpp
@@ -31,7 +31,9 @@ wxMemoryInputStream::wxMemoryInputStream(const char *data, size_t len)
   : wxInputStream()
 {
   m_i_streambuf->SetBufferIO((char*) data, (char*) (data+len));
+  m_i_streambuf->SetIntPosition(0); // seek to start pos
   m_i_streambuf->Fixed(TRUE);
+  m_length = len;
 }
 
 wxMemoryInputStream::~wxMemoryInputStream()