diff --git a/src/testdir/test_vim9_class.vim b/src/testdir/test_vim9_class.vim
index 4b6a730..a8f161d 100644
--- a/src/testdir/test_vim9_class.vim
+++ b/src/testdir/test_vim9_class.vim
@@ -995,7 +995,7 @@
         def Method(count: number)
       endinterface
   END
-  v9.CheckScriptFailure(lines, 'E1340: Argument already declared in the class: count')
+  v9.CheckScriptFailure(lines, 'E1340: Argument already declared in the class: count', 5)
 
   lines =<< trim END
       vim9script
@@ -1005,7 +1005,9 @@
         def Method(value: number)
       endinterface
   END
-  v9.CheckScriptFailure(lines, 'E1340: Argument already declared in the class: value')
+  # The argument name and the object member name are the same, but this is not a
+  # problem because object members are always accessed with the "this." prefix.
+  v9.CheckScriptSuccess(lines)
 
   lines =<< trim END
       vim9script