diff --git a/src/evalwindow.c b/src/evalwindow.c
index 492269e..e00747a 100644
--- a/src/evalwindow.c
+++ b/src/evalwindow.c
@@ -673,6 +673,10 @@
     win_T	*save_curwin;
     tabpage_T	*save_curtab;
 
+    // Return an empty string if something fails.
+    rettv->v_type = VAR_STRING;
+    rettv->vval.v_string = NULL;
+
     if (wp != NULL && tp != NULL)
     {
 	pos_T	curpos = wp->w_cursor;
diff --git a/src/testdir/test_execute_func.vim b/src/testdir/test_execute_func.vim
index e02b08e..0363717 100644
--- a/src/testdir/test_execute_func.vim
+++ b/src/testdir/test_execute_func.vim
@@ -89,6 +89,8 @@
   call win_gotoid(thiswin)
   let line = win_execute(otherwin, 'echo getline(1)')
   call assert_match('the new window', line)
+  let line = win_execute(134343, 'echo getline(1)')
+  call assert_equal('', line)
 
   if has('popupwin')
     let popupwin = popup_create('the popup win', {'line': 2, 'col': 3})
diff --git a/src/testdir/test_vim9_builtin.vim b/src/testdir/test_vim9_builtin.vim
index a84b7f6..40cfdcb 100644
--- a/src/testdir/test_vim9_builtin.vim
+++ b/src/testdir/test_vim9_builtin.vim
@@ -800,6 +800,11 @@
   timer_stop(id)
 enddef
 
+def Test_win_execute()
+  assert_equal("\n" .. winnr(), win_execute(win_getid(), 'echo winnr()'))
+  assert_equal('', win_execute(342343, 'echo winnr()'))
+enddef
+
 def Test_win_splitmove()
   split
   win_splitmove(1, 2, {vertical: true, rightbelow: true})
diff --git a/src/version.c b/src/version.c
index fe41ec2..24462a0 100644
--- a/src/version.c
+++ b/src/version.c
@@ -751,6 +751,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    2340,
+/**/
     2339,
 /**/
     2338,