--- a/hgext3rd/evolve/utility.py	Thu Oct 25 18:08:34 2018 +0200
+++ b/hgext3rd/evolve/utility.py	Thu Oct 25 18:09:08 2018 +0200
@@ -14,7 +14,7 @@
 from mercurial.node import nullrev
 
 shorttemplate = "[{label('evolve.rev', rev)}] {desc|firstline}\n"
-stacktemplate = "[s{label('evolve.rev', topicidx)}] {desc|firstline}\n"
+stacktemplate = """[{label('evolve.rev', if(topicidx, "s{topicidx}", rev))}] {desc|firstline}\n"""
 
 def obsexcmsg(ui, message, important=False):
     verbose = ui.configbool('experimental', 'verbose-obsolescence-exchange',