Motif L&F: Unable to reduce the width of JInternalFrame

In Motif L&F JInternalFrame's width can be increased by mouse drag but not reduced. While we can do that in other L&F's
 
  Steps to reproduce:
   a) Open SwingSet2, Change its L&F to Motif
   b) Create a new resizable JInternalFrame.
   c) Increase its width, It will work
   d) Now try reducing its width. It will not allow
      to reduce the width.