--- a/mercurial/merge.py	Mon Sep 11 13:03:27 2017 -0700
+++ b/mercurial/merge.py	Mon Sep 11 13:03:27 2017 -0700
@@ -1126,6 +1126,10 @@
                            "(consider changing to repo root: %s)\n") %
                          repo.root)
 
+    # It's necessary to flush here in case we're inside a worker fork and will
+    # quit after this function.
+    wctx.flushall()
+
 def batchget(repo, mctx, wctx, actions):
     """apply gets to the working directory
 
@@ -1161,6 +1165,10 @@
     if i > 0:
         yield i, f
 
+    # It's necessary to flush here in case we're inside a worker fork and will
+    # quit after this function.
+    wctx.flushall()
+
 def applyupdates(repo, actions, wctx, mctx, overwrite, labels=None):
     """apply the merge action list to the working directory
 
@@ -1229,6 +1237,10 @@
         progress(_updating, z, item=item, total=numupdates, unit=_files)
     removed = len(actions['r'])
 
+    # We should flush before forking into worker processes, since those workers
+    # flush when they complete, and we don't want to duplicate work.
+    wctx.flushall()
+
     # get in parallel
     prog = worker.worker(repo.ui, 0.001, batchget, (repo, mctx, wctx),
                          actions['g'])