diff --git a/src/cli/oneflow-template b/src/cli/oneflow-template
index 7110a3dba8..ddfbb51bdc 100755
--- a/src/cli/oneflow-template
+++ b/src/cli/oneflow-template
@@ -304,7 +304,7 @@ cmd=CommandParser::CmdParser.new(ARGV) do
         Instantiate a Service Template
     EOT
 
-    command :instantiate, instantiate_desc, :template_id,
+    command :instantiate, instantiate_desc, :template_id, [:file, nil],
             :options => [Service::JSON_FORMAT, Service::TOP] do
         client = Service::Client.new(
                     :username   => options[:username],
@@ -312,7 +312,13 @@ cmd=CommandParser::CmdParser.new(ARGV) do
                     :url        => options[:server],
                     :user_agent => USER_AGENT)
 
-        json_str = Service.build_json_action('instantiate')
+        params = Hash.new
+
+        if(args[1])
+            params['merge_template'] = File.read(args[1])
+        end
+
+        json_str = Service.build_json_action('instantiate', params)
 
         response = client.post("#{RESOURCE_PATH}/#{args[0]}/action", json_str)
 
diff --git a/src/flow/lib/models/service_template.rb b/src/flow/lib/models/service_template.rb
index 890b2ce0f1..92368ff2d2 100644
--- a/src/flow/lib/models/service_template.rb
+++ b/src/flow/lib/models/service_template.rb
@@ -171,14 +171,7 @@ module OpenNebula
         def allocate(template_json)
             template = JSON.parse(template_json)
 
-            validator = Validator::Validator.new(
-                :default_values => true,
-                :delete_extra_properties => false
-            )
-
-            validator.validate!(template, SCHEMA)
-
-            validate_values(template)
+            validate(template)
 
             super(template.to_json, template['name'])
         end
@@ -193,6 +186,12 @@ module OpenNebula
         def update(template_json)
             template = JSON.parse(template_json)
 
+            validator(template)
+
+            super(template.to_json)
+        end
+
+        def self.validate(template)
             validator = Validator::Validator.new(
                 :default_values => true,
                 :delete_extra_properties => false
@@ -201,13 +200,11 @@ module OpenNebula
             validator.validate!(template, SCHEMA)
 
             validate_values(template)
-
-            super(template.to_json)
         end
 
     private
 
-        def validate_values(template)
+        def self.validate_values(template)
             parser = ElasticityGrammarParser.new
 
             roles = template['roles']
diff --git a/src/flow/oneflow-server.rb b/src/flow/oneflow-server.rb
index 656eef571b..eb5d5c924c 100644
--- a/src/flow/oneflow-server.rb
+++ b/src/flow/oneflow-server.rb
@@ -416,8 +416,29 @@ post '/service_template/:id/action' do
             error CloudServer::HTTP_ERROR_CODE[rc.errno], rc.message
         end
 
+        merge_template = opts['merge_template']
+
+        if !merge_template.nil?
+            begin
+                template = JSON.parse(merge_template)
+                orig_template = JSON.parse(service_template.template)
+
+                instantiate_template = orig_template.merge(template)
+
+                ServiceTemplate.validate(instantiate_template)
+
+                instantiate_template = instantiate_template.to_json
+
+            rescue Validator::ParseException, JSON::ParserError
+                error 400, $!.message
+            end
+        else
+            instantiate_template = service_template.template
+        end
+
+
         service = OpenNebula::Service.new(OpenNebula::Service.build_xml, @client)
-        rc = service.allocate(service_template.template)
+        rc = service.allocate(instantiate_template)
         if OpenNebula.is_error?(rc)
             error CloudServer::HTTP_ERROR_CODE[rc.errno], rc.message
         end