diff --git a/mercurial/cmdutil.py b/mercurial/cmdutil.py
--- a/mercurial/cmdutil.py
+++ b/mercurial/cmdutil.py
@@ -2765,9 +2765,6 @@ def revert(ui, repo, ctx, parents, *pats
             (unknown,       actions['unknown'],  discard),
             )
 
-        needdata = ('revert', 'add', 'undelete')
-        _revertprefetch(repo, ctx, *[actions[name][0] for name in needdata])
-
         wctx = repo[None]
         for abs, (rel, exact) in sorted(names.items()):
             # target file to be touch on disk (relative to cwd)
@@ -2797,6 +2794,9 @@ def revert(ui, repo, ctx, parents, *pats
 
 
         if not opts.get('dry_run'):
+            needdata = ('revert', 'add', 'undelete')
+            _revertprefetch(repo, ctx, *[actions[name][0] for name in needdata])
+
             _performrevert(repo, parents, ctx, actions)
 
             # get the list of subrepos that must be reverted