diff --git a/src/testdir/test_vim9_assign.vim b/src/testdir/test_vim9_assign.vim
index a26867f..cba7972 100644
--- a/src/testdir/test_vim9_assign.vim
+++ b/src/testdir/test_vim9_assign.vim
@@ -1906,6 +1906,12 @@
       unlet g:count
   END
   CheckDefAndScriptSuccess(lines)
+
+  lines =<< trim END
+      var nr = 7
+      ++ nr
+  END
+  CheckDefAndScriptFailure(lines, "E1202: No white space allowed after '++': ++ nr")
 enddef