diff --git a/src/testdir/test_vim9_builtin.vim b/src/testdir/test_vim9_builtin.vim
index 24a7f95..01f29d9 100644
--- a/src/testdir/test_vim9_builtin.vim
+++ b/src/testdir/test_vim9_builtin.vim
@@ -371,10 +371,17 @@
   assert_fails('bufname([])', 'E1220:')
 enddef
 
+let s:bufnr_res = 0
+
 def Test_bufnr()
   var buf = bufnr()
   bufnr('%')->assert_equal(buf)
 
+  # check the lock is not taken over through the stack
+  const nr = 10
+  bufnr_res = bufnr()
+  bufnr_res = 12345
+
   buf = bufnr('Xdummy', true)
   buf->assert_notequal(-1)
   exe 'bwipe! ' .. buf
diff --git a/src/version.c b/src/version.c
index 9d3afeb..fe7f299 100644
--- a/src/version.c
+++ b/src/version.c
@@ -751,6 +751,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    4643,
+/**/
     4642,
 /**/
     4641,
diff --git a/src/vim9execute.c b/src/vim9execute.c
index a95a488..c5dc30d 100644
--- a/src/vim9execute.c
+++ b/src/vim9execute.c
@@ -937,6 +937,7 @@
     tv = STACK_TV_BOT(-1);
     tv->v_type = VAR_NUMBER;
     tv->vval.v_number = 0;
+    tv->v_lock = 0;
 
     return OK;
 }