diff --git a/Gemfile.lock b/Gemfile.lock
index 3c70d78c7..c7a2ee9d1 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -93,7 +93,7 @@ GEM
       latex-decode (~> 0.0)
     binding_of_caller (0.8.0)
       debug_inspector (>= 0.0.1)
-    bolognese (1.0.35)
+    bolognese (1.0.36)
       activesupport (>= 4.2.5, < 6)
       benchmark_methods (~> 0.7)
       bibtex-ruby (~> 4.1)
@@ -284,7 +284,7 @@ GEM
       rest-client (~> 2.0.2)
     marcel (0.3.3)
       mimemagic (~> 0.3.2)
-    maremma (4.2)
+    maremma (4.2.1)
       activesupport (>= 4.2.5, < 6)
       addressable (>= 2.3.6)
       builder (~> 3.2, >= 3.2.2)
diff --git a/app/models/doi.rb b/app/models/doi.rb
index 21a4d030f..75fa7c4a9 100644
--- a/app/models/doi.rb
+++ b/app/models/doi.rb
@@ -186,13 +186,15 @@ class Doi < ActiveRecord::Base
     }
     indexes :rights_list,                    type: :object, properties: {
       rights: { type: :keyword },
-      rightsUri: { type: :keyword }
+      rightsUri: { type: :keyword },
+      lang: { type: :keyword }
     }
     indexes :subjects,                       type: :object, properties: {
       subject: { type: :keyword },
       subjectScheme: { type: :keyword },
       schemeUri: { type: :keyword },
-      valueUri: { type: :keyword }
+      valueUri: { type: :keyword },
+      lang: { type: :keyword }
     }
     indexes :container,                     type: :object, properties: {
       type: { type: :keyword },
diff --git a/config/initializers/_version.rb b/config/initializers/_version.rb
index a2ca6f086..b7b9ff914 100644
--- a/config/initializers/_version.rb
+++ b/config/initializers/_version.rb
@@ -1,5 +1,5 @@
 module Lupo
   class Application
-    VERSION = "2.3.6"
+    VERSION = "2.3.7"
   end
 end
\ No newline at end of file