diff -r 1726a53a8494 -r dfca84970da8 mercurial/merge.py
--- a/mercurial/merge.py	Fri Jan 15 01:20:47 2021 +0100
+++ b/mercurial/merge.py	Mon May 18 17:29:53 2020 -0400
@@ -1920,7 +1920,7 @@
             if len(pl) > 1:
                 raise error.Abort(_(b"outstanding uncommitted merge"))
             ms = wc.mergestate()
-            if list(ms.unresolved()):
+            if ms.unresolvedcount():
                 raise error.Abort(
                     _(b"outstanding merge conflicts"),
                     hint=_(b"use 'hg resolve' to resolve"),