Debug Sampler - Regular Expression Extractor - Response Assertion

Hi all,

I have a JMeter Test Plan with a Debug Sampler that prints out
system.properties file and others. Below of the Debug Sampler are a Regular
Expression Extractor that defines a variable FOO. This variable is checked
in a Response Assertion if it contains the result of the regex.

My variable result is always null.

How come?

Thanks
Gerrit