--- a/mercurial/merge.py	Wed May 11 09:34:59 2016 +0200
+++ b/mercurial/merge.py	Wed May 11 09:31:47 2016 +0200
@@ -1442,7 +1442,7 @@
             pas = [repo[ancestor]]
 
         if node is None:
-            repo.ui.develwarn('update with no target', 'oldapi')
+            repo.ui.deprecwarn('update with no target', '3.9')
             rev, _mark, _act = destutil.destupdate(repo)
             node = repo[rev].node()