diff --git a/hgext/remotefilelog/repack.py b/hgext/remotefilelog/repack.py
--- a/hgext/remotefilelog/repack.py
+++ b/hgext/remotefilelog/repack.py
@@ -43,7 +43,8 @@ def backgroundrepack(repo, incremental=T
     if packsonly:
         cmd.append('--packsonly')
     repo.ui.warn(msg)
-    procutil.runbgcommand(cmd, encoding.environ)
+    # We know this command will find a binary, so don't block on it starting.
+    procutil.runbgcommand(cmd, encoding.environ, ensurestart=False)
 
 def fullrepack(repo, options=None):
     """If ``packsonly`` is True, stores creating only loose objects are skipped.
diff --git a/hgext/remotefilelog/shallowrepo.py b/hgext/remotefilelog/shallowrepo.py
--- a/hgext/remotefilelog/shallowrepo.py
+++ b/hgext/remotefilelog/shallowrepo.py
@@ -190,7 +190,9 @@ def wraprepo(repo):
                 cmd.append('--repack')
             if revs:
                 cmd += ['-r', revs]
-            procutil.runbgcommand(cmd, encoding.environ)
+            # We know this command will find a binary, so don't block
+            # on it starting.
+            procutil.runbgcommand(cmd, encoding.environ, ensurestart=False)
 
         def prefetch(self, revs, base=None, pats=None, opts=None):
             """Prefetches all the necessary file revisions for the given revs