diff --git a/lib/redmine/syntax_highlighting.rb b/lib/redmine/syntax_highlighting.rb
index 4380627ac..feff4f6b7 100644
--- a/lib/redmine/syntax_highlighting.rb
+++ b/lib/redmine/syntax_highlighting.rb
@@ -55,6 +55,17 @@ module Redmine
     module CodeRay
       require 'coderay'
 
+      def self.retrieve_supported_languages
+        ::CodeRay::Scanners.list +
+        # Add CodeRay scanner aliases
+        ::CodeRay::Scanners.plugin_hash.keys.map(&:to_sym) -
+        # Remove internal CodeRay scanners
+        %w(debug default raydebug scanner).map(&:to_sym)
+      end
+      private_class_method :retrieve_supported_languages
+
+      SUPPORTED_LANGUAGES = retrieve_supported_languages
+
       class << self
         # Highlights +text+ as the content of +filename+
         # Should not return line numbers nor outer pre tag
@@ -70,10 +81,7 @@ module Redmine
         end
 
         def language_supported?(language)
-          supported_languages =
-            ::CodeRay::Scanners.list +
-            ::CodeRay::Scanners.plugin_hash.keys.map(&:to_sym)
-          supported_languages.include?(language.to_s.downcase.to_sym)
+          SUPPORTED_LANGUAGES.include?(language.to_s.downcase.to_sym)
         rescue
           false
         end
diff --git a/test/unit/helpers/application_helper_test.rb b/test/unit/helpers/application_helper_test.rb
index 4b7eaea42..c82922cd0 100644
--- a/test/unit/helpers/application_helper_test.rb
+++ b/test/unit/helpers/application_helper_test.rb
@@ -1020,20 +1020,6 @@ EXPECTED
     assert_equal expected.gsub(%r{[\r\n\t]}, ''), textilizable(raw).gsub(%r{[\r\n\t]}, '')
   end
 
-  def test_syntax_highlight_by_coderay_alias
-    raw = <<-RAW
-<pre><code class="ecma_script">
-alert("hello, world");
-</code></pre>
-RAW
-
-    expected = <<-EXPECTED
-<pre><code class=\"ecma_script syntaxhl\"><span class=\"CodeRay\">alert(<span class=\"string\"><span class=\"delimiter\">&quot;</span><span class=\"content\">hello, world</span><span class=\"delimiter\">&quot;</span></span>);</span></code></pre>
-EXPECTED
-
-    assert_equal expected.gsub(%r{[\r\n\t]}, ''), textilizable(raw).gsub(%r{[\r\n\t]}, '')
-  end
-
   def test_to_path_param
     assert_equal 'test1/test2', to_path_param('test1/test2')
     assert_equal 'test1/test2', to_path_param('/test1/test2/')
diff --git a/test/unit/lib/redmine/syntax_highlighting/coderay_test.rb b/test/unit/lib/redmine/syntax_highlighting/coderay_test.rb
new file mode 100644
index 000000000..5374172f7
--- /dev/null
+++ b/test/unit/lib/redmine/syntax_highlighting/coderay_test.rb
@@ -0,0 +1,37 @@
+# Redmine - project management software
+# Copyright (C) 2006-2016  Jean-Philippe Lang
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License
+# as published by the Free Software Foundation; either version 2
+# of the License, or (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+
+require File.expand_path('../../../../../test_helper', __FILE__)
+
+class Redmine::SyntaxHighlighting::CodeRayTest < ActiveSupport::TestCase
+  def test_retrieve_supported_languages_should_return_array_of_symbols
+    assert_kind_of Array, Redmine::SyntaxHighlighting::CodeRay.send(:retrieve_supported_languages)
+    assert_kind_of Symbol, Redmine::SyntaxHighlighting::CodeRay.send(:retrieve_supported_languages).first
+  end
+
+  def test_retrieve_supported_languages_should_return_array_of_symbols_holding_languages
+    assert_includes Redmine::SyntaxHighlighting::CodeRay.send(:retrieve_supported_languages), :ruby
+  end
+
+  def test_retrieve_supported_languages_should_return_array_of_symbols_holding_languages_aliases
+    assert_includes Redmine::SyntaxHighlighting::CodeRay.send(:retrieve_supported_languages), :javascript
+  end
+
+  def test_retrieve_supported_languages_should_return_array_of_symbols_not_holding_internal_languages
+    refute_includes Redmine::SyntaxHighlighting::CodeRay.send(:retrieve_supported_languages), :default
+  end
+end