diff --git a/mercurial/commands.py b/mercurial/commands.py
--- a/mercurial/commands.py
+++ b/mercurial/commands.py
@@ -4210,7 +4210,8 @@ def phase(ui, repo, *revs, **opts):
 
         public < draft < secret
 
-    Return 0 on success, 1 if no phases were changed.
+    Return 0 on success, 1 if no phases were changed or some could not
+    be changed.
     """
     # search for a unique phase argument
     targetphase = None
@@ -4252,8 +4253,18 @@ def phase(ui, repo, *revs, **opts):
             changes = 0
             newdata = repo._phaserev
             changes = sum(o != newdata[i] for i, o in enumerate(olddata))
+            rejected = [n for n in nodes
+                        if newdata[repo[n].rev()] < targetphase]
+            if rejected:
+                ui.warn(_('cannot move %i changesets to a more permissive '
+                          'phase, use --force\n') % len(rejected))
+                ret = 1
             if changes:
-                ui.note(_('phase change for %i changesets\n') % changes)
+                msg = _('phase changed for %i changesets\n') % changes
+                if ret:
+                    ui.status(msg)
+                else:
+                    ui.note(msg)
             else:
                 ui.warn(_('no phases changed\n'))
                 ret = 1
diff --git a/tests/test-phases.t b/tests/test-phases.t
--- a/tests/test-phases.t
+++ b/tests/test-phases.t
@@ -402,3 +402,34 @@ move changeset forward and backward
   |
   o  0 public A
   
+test partial failure
+
+  $ hg phase --public 7
+  $ hg phase --draft '5 or 7'
+  cannot move 1 changesets to a more permissive phase, use --force
+  phase changed for 1 changesets
+  [1]
+  $ hg log -G --template "{rev} {phase} {desc}\n"
+  @    7 public merge B' and E
+  |\
+  | o  6 public B'
+  | |
+  +---o  5 draft H
+  | |
+  o |  4 public E
+  | |
+  o |  3 public D
+  | |
+  o |  2 public C
+  |/
+  o  1 public B
+  |
+  o  0 public A
+  
+
+test complete failure
+
+  $ hg phase --draft 7
+  cannot move 1 changesets to a more permissive phase, use --force
+  no phases changed
+  [1]