diff --git a/test/ruby/test_syntax.rb b/test/ruby/test_syntax.rb
index 35c70254bf..8b89f95dc4 100644
--- a/test/ruby/test_syntax.rb
+++ b/test/ruby/test_syntax.rb
@@ -186,6 +186,12 @@ class TestSyntax < Test::Unit::TestCase
     assert_valid_syntax("def self; :foo; end", __FILE__, bug6403)
   end
 
+  def test_unassignable
+    %w[self nil true false __FILE__ __LINE__ __ENCODING__].each do |kwd|
+      assert_raise(SyntaxError) {eval("#{kwd} = nil")}
+    end
+  end
+
   private
 
   def not_label(x) @result = x; @not_label ||= nil end