--- a/mercurial/debugcommands.py	Wed Mar 14 15:44:53 2018 -0400
+++ b/mercurial/debugcommands.py	Wed Feb 21 17:16:56 2018 +0100
@@ -345,11 +345,14 @@
         if part.type == 'changegroup':
             version = part.params.get('version', '01')
             cg = changegroup.getunbundler(version, part, 'UN')
-            _debugchangegroup(ui, cg, all=all, indent=4, **opts)
+            if not ui.quiet:
+                _debugchangegroup(ui, cg, all=all, indent=4, **opts)
         if part.type == 'obsmarkers':
-            _debugobsmarkers(ui, part, indent=4, **opts)
+            if not ui.quiet:
+                _debugobsmarkers(ui, part, indent=4, **opts)
         if part.type == 'phase-heads':
-            _debugphaseheads(ui, part, indent=4)
+            if not ui.quiet:
+                _debugphaseheads(ui, part, indent=4)
 
 @command('debugbundle',
         [('a', 'all', None, _('show all details')),

--- a/tests/test-debugbundle.t	Wed Mar 14 15:44:53 2018 -0400
+++ b/tests/test-debugbundle.t	Wed Feb 21 17:16:56 2018 +0100
@@ -35,6 +35,12 @@
       0e067c57feba1a5694ca4844f05588bb1bf82342
       991a3460af53952d10ec8a295d3d2cc2e5fa9690
 
+Quiet output
+
+  $ hg debugbundle --quiet bundle2.hg
+  Stream params: {}
+  changegroup -- {nbchanges: 2, version: 02}
+
 Verbose output:
 
   $ hg debugbundle --all bundle.hg