diff --git a/mercurial/bundle2.py b/mercurial/bundle2.py
--- a/mercurial/bundle2.py
+++ b/mercurial/bundle2.py
@@ -2033,7 +2033,7 @@ def handlebookmark(op, inpart):
             for book, node in changes:
                 hookargs = tr.hookargs.copy()
                 hookargs['pushkeycompat'] = '1'
-                hookargs['namespace'] = 'bookmark'
+                hookargs['namespace'] = 'bookmarks'
                 hookargs['key'] = book
                 hookargs['old'] = nodemod.hex(bookstore.get(book, ''))
                 hookargs['new'] = nodemod.hex(node if node is not None else '')
diff --git a/tests/test-bookmarks-pushpull.t b/tests/test-bookmarks-pushpull.t
--- a/tests/test-bookmarks-pushpull.t
+++ b/tests/test-bookmarks-pushpull.t
@@ -1173,3 +1173,72 @@ Using http
 
   $ hg -R ../issue4455-dest/ bookmarks
   no bookmarks set
+
+  $ cd ..
+
+Test that pre-pushkey compat for bookmark works as expected (issue5777)
+
+  $ cat << EOF >> $HGRCPATH
+  > [ui]
+  > ssh="$PYTHON" "$TESTDIR/dummyssh"
+  > [server]
+  > bookmarks-pushkey-compat = yes
+  > EOF
+
+  $ hg init server
+  $ echo foo > server/a
+  $ hg -R server book foo
+  $ hg -R server commit -Am a
+  adding a
+  $ hg clone ssh://user@dummy/server client
+  requesting all changes
+  adding changesets
+  adding manifests
+  adding file changes
+  added 1 changesets with 1 changes to 1 files
+  new changesets 79513d0d7716
+  updating to branch default
+  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+
+Forbid bookmark move on the server
+
+  $ cat << EOF >> server/.hg/hgrc
+  > [hooks]
+  > prepushkey.no-bm-move= echo \$HG_NAMESPACE | grep -v bookmarks
+  > EOF
+
+pushing changeset is okay
+
+  $ echo bar >> client/a
+  $ hg -R client commit -m b
+  $ hg -R client push
+  pushing to ssh://user@dummy/server
+  searching for changes
+  remote: adding changesets
+  remote: adding manifests
+  remote: adding file changes
+  remote: added 1 changesets with 1 changes to 1 files
+
+attempt to move the bookmark is rejected
+
+  $ hg -R client book foo -r .
+  moving bookmark 'foo' forward from 79513d0d7716
+
+#if b2-pushkey
+  $ hg -R client push
+  pushing to ssh://user@dummy/server
+  searching for changes
+  no changes found
+  remote: pushkey-abort: prepushkey.no-bm-move hook exited with status 1
+  abort: updating bookmark foo failed!
+  [255]
+#endif
+#if b2-binary
+  $ hg -R client push
+  pushing to ssh://user@dummy/server
+  searching for changes
+  no changes found
+  remote: prepushkey.no-bm-move hook exited with status 1
+  abort: push failed on remote
+  [255]
+#endif
diff --git a/tests/test-bundle2-exchange.t b/tests/test-bundle2-exchange.t
--- a/tests/test-bundle2-exchange.t
+++ b/tests/test-bundle2-exchange.t
@@ -253,7 +253,7 @@ push
   remote: added 1 changesets with 0 changes to 0 files (-1 heads)
   remote: 1 new obsolescence markers
   remote: pre-close-tip:eea13746799a public book_eea1
-  remote: pushkey: lock state after "bookmark"
+  remote: pushkey: lock state after "bookmarks"
   remote: lock:  free
   remote: wlock: free
   remote: postclose-tip:eea13746799a public book_eea1
@@ -339,7 +339,7 @@ push over ssh
   remote: added 1 changesets with 1 changes to 1 files
   remote: 1 new obsolescence markers
   remote: pre-close-tip:5fddd98957c8 draft book_5fdd
-  remote: pushkey: lock state after "bookmark"
+  remote: pushkey: lock state after "bookmarks"
   remote: lock:  free
   remote: wlock: free
   remote: postclose-tip:5fddd98957c8 draft book_5fdd
@@ -390,7 +390,7 @@ push over http
   remote: added 1 changesets with 1 changes to 1 files
   remote: 1 new obsolescence markers
   remote: pre-close-tip:32af7686d403 public book_32af
-  remote: pushkey: lock state after "bookmark"
+  remote: pushkey: lock state after "bookmarks"
   remote: lock:  free
   remote: wlock: free
   remote: postclose-tip:32af7686d403 public book_32af
diff --git a/tests/test-hook.t b/tests/test-hook.t
--- a/tests/test-hook.t
+++ b/tests/test-hook.t
@@ -244,7 +244,7 @@ pushkey hook
   no changes found
   pretxnopen hook: HG_HOOKNAME=pretxnopen HG_HOOKTYPE=pretxnopen HG_TXNID=TXN:$ID$ HG_TXNNAME=push
   pretxnclose hook: HG_BOOKMARK_MOVED=1 HG_BUNDLE2=1 HG_HOOKNAME=pretxnclose HG_HOOKTYPE=pretxnclose HG_PENDING=$TESTTMP/a HG_SOURCE=push HG_TXNID=TXN:$ID$ HG_TXNNAME=push HG_URL=file:$TESTTMP/a
-  pushkey hook: HG_BUNDLE2=1 HG_HOOKNAME=pushkey HG_HOOKTYPE=pushkey HG_KEY=foo HG_NAMESPACE=bookmark HG_NEW=0000000000000000000000000000000000000000 HG_PUSHKEYCOMPAT=1 HG_SOURCE=push HG_TXNID=TXN:$ID$ HG_URL=file:$TESTTMP/a
+  pushkey hook: HG_BUNDLE2=1 HG_HOOKNAME=pushkey HG_HOOKTYPE=pushkey HG_KEY=foo HG_NAMESPACE=bookmarks HG_NEW=0000000000000000000000000000000000000000 HG_PUSHKEYCOMPAT=1 HG_SOURCE=push HG_TXNID=TXN:$ID$ HG_URL=file:$TESTTMP/a
   txnclose hook: HG_BOOKMARK_MOVED=1 HG_BUNDLE2=1 HG_HOOKNAME=txnclose HG_HOOKTYPE=txnclose HG_SOURCE=push HG_TXNID=TXN:$ID$ HG_TXNNAME=push HG_URL=file:$TESTTMP/a
   exporting bookmark foo
   [1]
@@ -281,7 +281,7 @@ test that prepushkey can prevent incomin
   listkeys hook: HG_HOOKNAME=listkeys HG_HOOKTYPE=listkeys HG_NAMESPACE=bookmarks HG_VALUES={'bar': '0000000000000000000000000000000000000000', 'foo': '0000000000000000000000000000000000000000'}
   no changes found
   pretxnopen hook: HG_HOOKNAME=pretxnopen HG_HOOKTYPE=pretxnopen HG_TXNID=TXN:$ID$ HG_TXNNAME=push
-  prepushkey.forbid hook: HG_BUNDLE2=1 HG_HOOKNAME=prepushkey HG_HOOKTYPE=prepushkey HG_KEY=baz HG_NAMESPACE=bookmark HG_NEW=0000000000000000000000000000000000000000 HG_PUSHKEYCOMPAT=1 HG_SOURCE=push HG_TXNID=TXN:$ID$ HG_URL=file:$TESTTMP/a
+  prepushkey.forbid hook: HG_BUNDLE2=1 HG_HOOKNAME=prepushkey HG_HOOKTYPE=prepushkey HG_KEY=baz HG_NAMESPACE=bookmarks HG_NEW=0000000000000000000000000000000000000000 HG_PUSHKEYCOMPAT=1 HG_SOURCE=push HG_TXNID=TXN:$ID$ HG_URL=file:$TESTTMP/a
   abort: prepushkey hook exited with status 1
   [255]
   $ cd ../a