diff --git a/mercurial/utils/procutil.py b/mercurial/utils/procutil.py
--- a/mercurial/utils/procutil.py
+++ b/mercurial/utils/procutil.py
@@ -273,13 +273,13 @@ def protectstdio(uin, uout):
     """
     uout.flush()
     fin, fout = uin, uout
-    if uin is stdin:
+    if _testfileno(uin, stdin):
         newfd = os.dup(uin.fileno())
         nullfd = os.open(os.devnull, os.O_RDONLY)
         os.dup2(nullfd, uin.fileno())
         os.close(nullfd)
         fin = os.fdopen(newfd, r'rb')
-    if uout is stdout:
+    if _testfileno(uout, stdout):
         newfd = os.dup(uout.fileno())
         os.dup2(stderr.fileno(), uout.fileno())
         fout = os.fdopen(newfd, r'wb')
diff --git a/tests/test-ssh.t b/tests/test-ssh.t
--- a/tests/test-ssh.t
+++ b/tests/test-ssh.t
@@ -328,6 +328,10 @@ try again with remote chg, which should 
   pushing to ssh://user@dummy/remote
   searching for changes
   remote has heads on branch 'default' that are not known locally: 6c0482d977a3
+  remote: adding changesets
+  remote: adding manifests
+  remote: adding file changes
+  remote: added 1 changesets with 1 changes to 1 files
   abort: not a Mercurial bundle
   [255]