diff --git a/mercurial/ui.py b/mercurial/ui.py
--- a/mercurial/ui.py
+++ b/mercurial/ui.py
@@ -962,6 +962,7 @@
             # formatted() will need some adjustment.
             or not self.formatted()
             or self.plain()
+            or self._buffers
             # TODO: expose debugger-enabled on the UI object
             or '--debugger' in pycompat.sysargv):
             # We only want to paginate if the ui appears to be
diff --git a/tests/test-pager.t b/tests/test-pager.t
--- a/tests/test-pager.t
+++ b/tests/test-pager.t
@@ -340,6 +340,20 @@
    9: a 9
   10: a 10
 
+During pushbuffer, pager should not start:
+  $ cat > $TESTTMP/pushbufferpager.py <<EOF
+  > def uisetup(ui):
+  >     ui.pushbuffer()
+  >     ui.pager('mycmd')
+  >     ui.write('content\n')
+  >     ui.write(ui.popbuffer())
+  > EOF
+
+  $ echo append >> a
+  $ hg --config extensions.pushbuffer=$TESTTMP/pushbufferpager.py status --color=off
+  content
+  paged! 'M a\n'
+
 Environment variables like LESS and LV are set automatically:
   $ cat > $TESTTMP/printlesslv.py <<EOF
   > from __future__ import absolute_import