simple predicate header

I am trying to get a choice based on the value in a header:

<choice>
<when>
<simple> ${header.Authorization} == 'enabled' </simple>

where when I log the value with :
<log message="***************** ${header.Authorization}***************" />

I get
3:55:05,022 INFO [proxy] (qtp1271679061-127) *****************
enabled***************

It does not work:

Caused by:
org.apache.camel.language.simple.types.SimpleIllegalSyntaxException:
expected symbol whiteSpace but was singleQuote at location 25
${header.Authorization}=='enabled'

Could you please help?

Thank you