It 's a bug. The code in the method `initMemIndex` ( at NginxClojureRT.java ) ``` java KNOWN_REQ_HEADERS.put("X-Forwarded-For", safeBuildKnownTableEltHeaderHolder("X-Forwarded-For", NGX_HTTP_CLOJURE_HEADERSI_X_FORWARDED_FOR_OFFSET, NGX_HTTP_CLOJURE_HEADERSI_HEADERS_OFFSET)); ``` SHOULD BE changed to ``` java KNOWN_REQ_HEADERS.put("X-Forwarded-For", new ArrayHeaderHolder("X-Forwarded-For", NGX_HTTP_CLOJURE_HEADERSI_X_FORWARDED_FOR_OFFSET, NGX_HTTP_CLOJURE_HEADERSI_HEADERS_OFFSET)); ``` Then recompile the java source by lein ``` shell #Please check the lein version lein version, it should be at least 2.0.0. $ cd nginx-clojure $ lein jar ```