diff --git a/lib/docker-sync/sync_strategy/unison.rb b/lib/docker-sync/sync_strategy/unison.rb
index <HASH>..<HASH> 100644
--- a/lib/docker-sync/sync_strategy/unison.rb
+++ b/lib/docker-sync/sync_strategy/unison.rb
@@ -158,7 +158,7 @@ module Docker_Sync
       end
 
       def get_host_port(container_name, container_port)
-        cmd = 'docker inspect --format=" {{ .NetworkSettings.Ports }} " ' + container_name + ' | sed -r "s/.*map\[' + container_port + '[^ ]+\s([0-9]+).*/\1/"'
+        cmd = 'docker inspect --format=" {{ .NetworkSettings.Ports }} " ' + container_name + ' | /usr/bin/sed  -E "s/.*map\[' + container_port + '[^ ]+ ([0-9]*)[^0-9].*/\1/"'
         say_status 'command', cmd, :white if @options['verbose']
         stdout, stderr, exit_status = Open3.capture3(cmd)
         if not exit_status.success?
[BUGFIX] Unison reports too many roots

- PB: the sed expression to grab the used port in container is not
compatible with the default sed binary.
- FIX: force the use of the default sed binary /usr/bin/sed and update
the regexp accordingly