diff --git a/app/models/dmsf_title_query_column.rb b/app/models/dmsf_title_query_column.rb
index 000c3932..7edc637c 100644
--- a/app/models/dmsf_title_query_column.rb
+++ b/app/models/dmsf_title_query_column.rb
@@ -20,6 +20,8 @@
 # Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 #
 
+require 'query'
+
 class DmsfTitleQueryColumn < QueryColumn
 
   def css_classes
diff --git a/app/models/dmsf_version_query_column.rb b/app/models/dmsf_version_query_column.rb
index 6e74ddaa..6821a262 100644
--- a/app/models/dmsf_version_query_column.rb
+++ b/app/models/dmsf_version_query_column.rb
@@ -20,6 +20,8 @@
 # Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 #
 
+require 'query'
+
 class DmsfVersionQueryColumn < QueryColumn
 
   def value_object(object)