diff --git a/src/flow/Gemfile.lock b/src/flow/Gemfile.lock
index 886395dcfe..29983397c1 100644
--- a/src/flow/Gemfile.lock
+++ b/src/flow/Gemfile.lock
@@ -12,7 +12,7 @@ GEM
       rack-protection (~> 1.2)
       tilt (~> 1.3, >= 1.3.3)
     tilt (1.3.3)
-    treetop (1.4.12)
+    treetop (>= 1.6.3)
       polyglot
       polyglot (>= 0.3.1)
     xml-simple (1.1.1)
diff --git a/src/flow/lib/models/role.rb b/src/flow/lib/models/role.rb
index ecfa69fe86..850449461c 100644
--- a/src/flow/lib/models/role.rb
+++ b/src/flow/lib/models/role.rb
@@ -18,6 +18,10 @@ require 'treetop'
 require 'grammar'
 require 'parse-cron'
 
+if !(Gem.loaded_specs['treetop'].version >= Gem::Version.create('1.6.3'))
+    raise "treetop gem version must be >= 1.6.3"
+end
+
 module OpenNebula
     class Role