def'd haml-engine cannot be eval'd via the REPL?

gistfile1.clj

(ns blog.core
  (:require [ring.adapter.jetty :as jetty]
            [clojure.contrib.io :as io]
            [clojure.contrib.classpath :as cp])
  (:import [org.jruby.embed ScriptingContainer LocalContextScope]))

(def scripting-container (ScriptingContainer. LocalContextScope/THREADSAFE))

(defn execute-rb [rb-string]
  (. scripting-container runScriptlet rb-string))

(gem-require "rubygems"
(gem-require "haml-3.1.3/gem/haml")

(def haml-engine (execute-rb "Haml::Engine")) ;; C-x C-e from the REPL says HAML is not defined
;; However, if I type this line out in the REPL, it works. Puzzling.