Shellshock - not vulnerable with bash version 4.1?

We have several Amazon servers. It has bash version 4.1.2. Kaspersky claims that all bash versions up to 4.3 are unsafe. When I do this test... env x='() { :;}; echo vulnerable' bash -c 'echo hello' ... it returns: hello, and even though Lifehacker says that I should get an error back: bash: warning: x: ignoring function definition attempt bash....., I guess the simple "hello" is good enough. Still I'm in doubt. Can you explain what info I can trust?