diff --git a/CHANGELOG.txt b/CHANGELOG.txt
index 2b14b1b3..bf5c312a 100644
--- a/CHANGELOG.txt
+++ b/CHANGELOG.txt
@@ -4,6 +4,7 @@
 
 == ruote - 2.1.12    not yet released
 
+- using Sourcify to store block participant's code as a string
 - CompositeStorage#delete bug fix (Thanks Claudio)
 - ParticipantList#register bug fix (Thanks 'sandbox')
 - StorageHistory#wfids and DefaultHistory#wfids
diff --git a/lib/ruote/svc/participant_list.rb b/lib/ruote/svc/participant_list.rb
index a271a32e..08e32da9 100644
--- a/lib/ruote/svc/participant_list.rb
+++ b/lib/ruote/svc/participant_list.rb
@@ -47,15 +47,19 @@ def initialize (context)
     #
     def register (name, participant, options, block)
 
+      klass = (participant || Ruote::BlockParticipant).to_s
+
       options = options.inject({}) { |h, (k, v)|
         h[k.to_s] = v.is_a?(Symbol) ? v.to_s : v
         h
       }
-      options['block'] = block.to_source if block
 
-      key = (name.is_a?(Regexp) ? name : Regexp.new("^#{name}$")).source
+      if block
+        options['block'] = block.to_source
+        @context.treechecker.block_check(options['block'])
+      end
 
-      klass = (participant || Ruote::BlockParticipant).to_s
+      key = (name.is_a?(Regexp) ? name : Regexp.new("^#{name}$")).source
 
       entry = [ key, [ klass, options ] ]
 
diff --git a/test/functional/ft_24_block_participant.rb b/test/functional/ft_24_block_participant.rb
index 6bca7725..4488e739 100644
--- a/test/functional/ft_24_block_participant.rb
+++ b/test/functional/ft_24_block_participant.rb
@@ -107,5 +107,15 @@ def test_raise_security_error_before_evaluating_rogue_code
 
     FileUtils.rm(fn) rescue nil
   end
+
+  def test_raise_security_error_upon_registering_rogue_block_participant
+
+    assert_raise Rufus::SecurityError do
+
+      @engine.register 'rogue' do |workitem|
+        workitem.content = File.read('test/nada.txt')
+      end
+    end
+  end
 end