diff --git a/remotefilelog/fileserverclient.py b/remotefilelog/fileserverclient.py
--- a/remotefilelog/fileserverclient.py
+++ b/remotefilelog/fileserverclient.py
@@ -20,6 +20,7 @@
     sshpeer,
     util,
 )
+from mercurial.utils import procutil
 
 from . import (
     constants,
@@ -150,7 +151,7 @@
         if self.pipeo:
             raise error.Abort(_("cache connection already open"))
         self.pipei, self.pipeo, self.pipee, self.subprocess = \
-            util.popen4(cachecommand)
+            procutil.popen4(cachecommand)
         self.connected = True
 
     def close(self):