diff --git a/src/testdir/test_vim9_assign.vim b/src/testdir/test_vim9_assign.vim
index 03427c8..b2f8fec 100644
--- a/src/testdir/test_vim9_assign.vim
+++ b/src/testdir/test_vim9_assign.vim
@@ -1392,6 +1392,14 @@
   [END]
   CheckScriptFailure(lines, 'E1145: Missing heredoc end marker: END')
   delfunc! g:Func
+
+  lines =<< trim END
+      var lines: number =<< trim STOP
+        aaa
+        bbb
+      STOP
+  END
+  CheckDefAndScriptFailure(lines, 'E1012: Type mismatch; expected number but got list<string>', 1)
 enddef
 
 def Test_var_func_call()