diff --git a/mercurial/destutil.py b/mercurial/destutil.py
--- a/mercurial/destutil.py
+++ b/mercurial/destutil.py
@@ -359,7 +359,7 @@
 
 def stackbase(ui, repo):
     revs = stack.getstack(repo)
-    return revs.last() if revs else None
+    return revs.first() if revs else None
 
 def _statusotherbook(ui, repo):
     bmheads = bookmarks.headsforactive(repo)
diff --git a/mercurial/stack.py b/mercurial/stack.py
--- a/mercurial/stack.py
+++ b/mercurial/stack.py
@@ -10,8 +10,8 @@
 from . import revsetlang, scmutil
 
 def getstack(repo, rev=None):
-    """return a smartrev of the stack containing either rev if it is not None
-    or the current working directory parent.
+    """return a sorted smartrev of the stack containing either rev if it is
+    not None or the current working directory parent.
 
     The stack will always contain all drafts changesets which are ancestors to
     the revision and are not merges.
@@ -21,4 +21,6 @@
 
     revspec = 'reverse(only(%s) and not public() and not ::merge())'
     revset = revsetlang.formatspec(revspec, rev)
-    return scmutil.revrange(repo, [revset])
+    revisions = scmutil.revrange(repo, [revset])
+    revisions.sort()
+    return revisions
diff --git a/tests/test-stack.t b/tests/test-stack.t
--- a/tests/test-stack.t
+++ b/tests/test-stack.t
@@ -57,8 +57,8 @@
   $ hg up other
   0 files updated, 0 files merged, 4 files removed, 0 files unresolved
   $ hg debugstack
+  0
   1
-  0
   $ hg phase --public 'branch("other")'
   $ hg debugstack
   $ hg up foo
@@ -72,10 +72,10 @@
   $ hg branch
   foo
   $ hg debugstack
+  2
+  3
+  4
   5
-  4
-  3
-  2
 
 Case with some of the branch unstable
 ------------------------------------
@@ -105,8 +105,8 @@
   $ hg up -r "desc(c_e)"
   2 files updated, 0 files merged, 0 files removed, 0 files unresolved
   $ hg debugstack
+  3
   4
-  3
   $ hg up -r "desc(c_d)"
   1 files updated, 0 files merged, 1 files removed, 0 files unresolved
 
@@ -167,13 +167,13 @@
 Test output
 
   $ hg debugstack
+  9
   10
-  9
   $ hg up 'desc(c_f)'
   2 files updated, 0 files merged, 2 files removed, 0 files unresolved
   $ hg debugstack
+  7
   8
-  7
 
 Case with multiple heads with unstability involved
 --------------------------------------------------