Environment variable in Logstash not being parsed correctly

Logstash 2.4 requires a command line argument of --allow-env to do environment substitutions.

Without the flag it doesn't complain (but doesn't work)

bin/logstash -f test.conf Settings: Default pipeline workers: 8Pipeline main started

With the flag, it will complain if you don't set it:

bin/logstash --allow-env -f test.conf  fetched an invalid config {:config=>"input {\n file {\n        path => \"/tmp/${RUN_ID}/*.txt\"\n        start_position => beginning\n        sincedb_path => \"/dev/null\"\n        ignore_older => 0\n    }\n}\n\noutput {\nstdout { codec=>rubydebug}\n elasticsearch {\n        hosts => [ \"localhost:9200\" ]\n        index => \"${RUN_ID}\"\n    }\n}\n\n\n", :reason=>"Cannot evaluate `${RUN_ID}`. Environment variable `RUN_ID` is not set and there is no default value given.", :level=>:error}

And of course with the argument and flag, everything works right:

export RUN_ID=10 bin/logstash --allow-env -f test.conf Pipeline main started{       "message" => "asdfasdf",      "@version" => "1",    "@timestamp" => "2016-11-01T21:10:15.964Z",          "path" => "/tmp/10/test.txt",          "host" => "XXXXXXXXX.local"}