It may be easier to just update the 5.1 image to the latest trunk version,
then save the morph after updating.

Be sure to save a copy of your image and changes files first, then
do the update as follows (it takes about 15 minutes or so):

  Go to Tools -> Preferences on the top menu bar to open a preference browser.
  In the preference browser, scroll down to "updates"
  Change Update URL from http://source.squeak.org/squeak51 to http://source.squeak.org/trunk (accept change)
  Close the preference browser
  Squeaky mouse -> Update Squeak (upper left corner on the menu bar)
  
  This will start the update process. You will encounter several merge
  dialog boxes, just accept all the merges and proceed in each of them
  until done:
  
  Merging Morphic-mt.1297, accept two changes, merge.
  Merging ST80-mt.217, accept change, merge.
  Merging ReleaseBuilder-mt.169, accept change, merge.
  Merging Morphic-tpr.1321, accept three changes, merge.
  ReleaseBuilder-eem.172, accept change, merge.
  
  ==> done.

Dave

On Sun, Jan 13, 2019 at 08:48:44PM +0100, karl ramberg wrote:
> There was some work done to the SmartRefenceStream loading and saving in
> 5.2.
> It was broken i 5.1 so I'm not quite sure how much you must do to make it
> work.
> I think it would be possible to back port the fixes if you can lokate them.
> 
> Best,
> Karl
> 
> 
> 
> 
> 
> On Sun, Jan 13, 2019 at 6:43 PM Philip Bernhart <philip.bernhart at posteo.de>
> wrote:
> 
> > Hi David,
> >
> > I tried to do an export / import again in the original
> > squeak5.1-16549-64bit-201608171728 derived image.
> >
> > And it failed there too. Creating empty morphs and
> > saving them / reloading them also fails when restoring
> > them. Doing the same on a squeak5.2 image seems to be
> > no problem.
> >
> > That's bad. As it makes it impossible? for me to migrate
> > objects created in an image to upgrade them to a new squeak
> > version (exporting them / reloading them).
> >
> > Suggestions?
> >
> >
> > Thanks,
> > Philip
> >
> > "David T. Lewis" <lewis at mail.msen.com> writes:
> >
> > > I can confirm the error, but I also see the same error when I try
> > > to load the morph file in a freshly downloaded Squeak5.1-16553-64bit
> > > image.
> > >
> > > Are you able to load the morph file back into the same image from
> > > which it was generated?
> > >
> > > If so, perhaps there is something that has been changed or added
> > > to that image that would need to be added to the new squeak 5.2
> > > image as well. This is only a guess, but maybe it will help.
> >
> >

>