diff --git a/mercurial/commands.py b/mercurial/commands.py
--- a/mercurial/commands.py
+++ b/mercurial/commands.py
@@ -5723,6 +5723,7 @@ def update(ui, repo, node=None, rev=None
             raise util.Abort(_("uncommitted local changes"))
         if not rev:
             rev = repo[repo[None].branch()].rev()
+        mergemod._checkunknown(repo, repo[None], repo[rev])
 
     if clean:
         ret = hg.clean(repo, rev)
diff --git a/mercurial/merge.py b/mercurial/merge.py
--- a/mercurial/merge.py
+++ b/mercurial/merge.py
@@ -545,6 +545,8 @@ def update(repo, node, branchmerge, forc
             if not force and (wc.files() or wc.deleted()):
                 raise util.Abort(_("outstanding uncommitted changes"),
                                  hint=_("use 'hg status' to list changes"))
+            if not force:
+                _checkunknown(repo, wc, p2)
             for s in wc.substate:
                 if wc.sub(s).dirty():
                     raise util.Abort(_("outstanding uncommitted changes in "
@@ -566,8 +568,6 @@ def update(repo, node, branchmerge, forc
         ### calculate phase
         action = []
         folding = not util.checkcase(repo.path)
-        if not force:
-            _checkunknown(repo, wc, p2)
         if folding:
             _checkcollision(p2, branchmerge and p1)
         action += _forgetremoved(wc, p2, branchmerge)