--- a/mercurial/merge.py	Wed Feb 24 19:31:55 2016 +0000
+++ b/mercurial/merge.py	Tue Feb 23 10:59:25 2016 -0800
@@ -801,10 +801,8 @@
 
     if '.hgsubstate' in m1:
         # check whether sub state is modified
-        for s in sorted(wctx.substate):
-            if wctx.sub(s).dirty():
-                m1['.hgsubstate'] += '+'
-                break
+        if any(wctx.sub(s).dirty() for s in wctx.substate):
+            m1['.hgsubstate'] += '+'
 
     # Compare manifests
     if matcher is not None: