svnadmin load issue about "svn:mergeinfo" property

  Hello,

I am merging multiple repositories with dump/load into a single one
and almost everything works well because the node structure in each
/trunk does not conflict.

To describe the situation:
repoA (1999 revisions): /trunk/appA
    with "svn:mergeinfo" containing "/branches/1.0:1000-1010" and
"/branches/featureX:800-820"
repoB (600 revisions in dump): /trunk/appB
    with "svn:mergeinfo" containing "/branches/1.0:500-505"

Both contains the same "/branches/2.0".

repoA: /branches/2.0
    with "svn:mergeinfo" containing "/branches/1.0:1000-1010" and
"/branches/featureX:800-820"
repoB: /branches/2.0
    with "svn:mergeinfo" containing "/branches/1.0:500-505"

I am loading a (filtered) dump of "repoB" into a copy of "repoA" and I
get the following result:

repoMerge (2599 revisions): /branches/2.0
   has "svn:mergeinfo" with only "/branches/1.0:2500-2505"

I would have expected the "svn:mergeinfo" to contain:
   /branches/1.0:1000-1010,2500-2505
   /branches/featureX:800-820

Am I wrong ? Is there anything I can do to work-around the issue or a
patch is required in "svnadmin load" ?

Thank you in advance for your help

--
Yves Martin