Following instructions in How to use multiple versions of unison on one system? I have used

unison -addversionno

to sync a Debian and Raspbian system, but received this error

Contacting server...
Fatal error: Received unexpected header from the server:
 expected "Unison 2.48\n" but received "bash: unison-2.48: command not found\n", 
which differs at "b".

It seems like the same versions are found but misinterpreted as incompatible.

What can I do to get it working?

I have also filed a bug on GitHub.

1 Answer 1


As it turned out in the discussion regarding the bug report -addversionno currently truncates the version info at the minor number.

I had installed


at the server and client (by copying the binary), but -addversionno was looking for


which did not exist.

As a workaround I created the symbolic link unison-2.48 pointing to unison-2.48.3.

ln -s unison-2.48.3 unison-2.48

Now it works as expected.

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