--- a/mercurial/hg.py Mon Feb 13 11:32:09 2017 -0800
+++ b/mercurial/hg.py Mon Feb 13 11:58:02 2017 -0800
@@ -739,6 +739,8 @@
if clean:
ret = _clean(repo, checkout)
else:
+ if check:
+ cmdutil.bailifchanged(repo, merge=False)
ret = _update(repo, checkout)
if not ret and movemarkfrom: