diff --git a/src/testdir/test_vim9_assign.vim b/src/testdir/test_vim9_assign.vim
index fa418b2..b8c6433 100644
--- a/src/testdir/test_vim9_assign.vim
+++ b/src/testdir/test_vim9_assign.vim
@@ -249,6 +249,13 @@
   END
 enddef
 
+def Test_reserved_name()
+  for name in ['true', 'false', 'null']
+    CheckDefExecAndScriptFailure(['var ' .. name .. ' =  0'], 'E1034:')
+    CheckDefExecAndScriptFailure(['var ' .. name .. ': bool'], 'E1034:')
+  endfor
+enddef
+
 def Test_skipped_assignment()
   var lines =<< trim END
       for x in []