diff --git a/plugins/virtuoso/lib/virtuoso_plugin/triples_management.rb b/plugins/virtuoso/lib/virtuoso_plugin/triples_management.rb
index 5140c9c..cc11bc5 100644
--- a/plugins/virtuoso/lib/virtuoso_plugin/triples_management.rb
+++ b/plugins/virtuoso/lib/virtuoso_plugin/triples_management.rb
@@ -18,15 +18,21 @@ class VirtuosoPlugin::TriplesManagement
   def update_triple(graph_uri, from_triple, to_triple)
     from_subject = from_triple[:subject]
     from_predicate = from_triple[:predicate]
-    from_object = from_triple[:object]
+    from_object = format_triple_term(from_triple[:object])
 
     to_subject = to_triple[:subject]
     to_predicate = to_triple[:predicate]
-    to_object = to_triple[:object]
+    to_object = format_triple_term(to_triple[:object])
 
-    query = "WITH <#{graph_uri}> DELETE { <#{from_subject}> <#{from_predicate}> '#{from_object}' } INSERT { <#{to_subject}> <#{to_predicate}> '#{to_object}' }"
+    query = "WITH <#{graph_uri}> DELETE { <#{from_subject}> <#{from_predicate}> #{from_object} } INSERT { <#{to_subject}> <#{to_predicate}> #{to_object} }"
 
     plugin.virtuoso_client.query(query)
   end
 
+  protected
+
+  def format_triple_term(term)
+    term =~ /^(http|https):\/\// ? "<#{term}>" : "'#{term}'"
+  end
+
 end
--
libgit2 0.21.2