diff --git a/app/flex/flex_search.yml b/app/flex/flex_search.yml
index 04b73ad5..f7189caa 100644
--- a/app/flex/flex_search.yml
+++ b/app/flex/flex_search.yml
@@ -7,6 +7,15 @@
 ANCHORS:
   - &name_locale_partial
     "name.<<locale>>^<<boost= 1>>"
+  - &species_support_id_partial
+    term:
+      species_support_id: <<species_support_id>>
+  - &occupied_zone_id_partial
+    terms:
+      occupied_zone_id: <<occupied_zone_id>>
+  - &restricted_zone_id_partial
+    terms:
+      restricted_zone_id: <<restricted_zone_id>>
 
 _name_locales:
   *name_locale_partial
@@ -14,6 +23,24 @@ _name_locales:
 _negative_name_locales:
   *name_locale_partial
 
+_species_support_ids:
+  *species_support_id_partial
+
+_negative_species_support_ids:
+  *species_support_id_partial
+
+_occupied_zone_ids:
+  *occupied_zone_id_partial
+
+_negative_occupied_zone_ids:
+  *occupied_zone_id_partial
+
+_restricted_zone_ids:
+  *restricted_zone_id_partial
+
+_negative_restricted_zone_ids:
+  *restricted_zone_id_partial
+
 item_search:
   - query:
       bool:
@@ -25,21 +52,15 @@ item_search:
               is_nc: <<is_nc= ~>>
           - term:
               is_pb: <<is_pb= ~>>
-          - term:
-              species_support_id: <<species_support_id= ~>>
-          - term:
-              occupied_zone_id: <<occupied_zone_id= ~>>
-          - term:
-              restricted_zone_id: <<restricted_zone_id= ~>>
+          - <<_species_support_ids= ~>>
+          - <<_occupied_zone_ids= ~>>
+          - <<_restricted_zone_ids= ~>>
         must_not:
-          - term:
-              species_support_id: <<negative_species_support_id= ~>>
-          - term:
-              occupied_zone_id: <<negative_occupied_zone_id= ~>>
-          - term:
-              restricted_zone_id: <<negative_restricted_zone_id= ~>>
           - multi_match:
               query: <<negative_name= ~>>
               fields: <<_negative_name_locales>>
+          - <<_negative_species_support_ids= ~>>
+          - <<_negative_occupied_zone_ids= ~>>
+          - <<_negative_restricted_zone_ids= ~>>
     sort:
       - name.<<locale>>.untouched
diff --git a/app/models/item/search/fields/set_field.rb b/app/models/item/search/fields/set_field.rb
index 3598e60a..e089fa13 100644
--- a/app/models/item/search/fields/set_field.rb
+++ b/app/models/item/search/fields/set_field.rb
@@ -8,35 +8,25 @@ class Item
         end
         
         def <<(filter)
-          if filter.value.respond_to?(:each)
-            filter.value.each do |value|
-              add_value(value, filter.positive?)
-            end
-          else
-            add_value(filter.value, filter.positive?)
+          if @values[!filter.positive?].include?(filter.value)
+            raise Item::Search::Contradiction,
+                  "positive #{key} and negative #{key} both contain #{filter.value}"
           end
+          
+          @values[filter.positive?] << filter.value
         end
         
         def to_flex_params
           {
-            key => nil_if_empty(@values[true]),
-            :"negative_#{key}" => nil_if_empty(@values[false])
+            :"_#{key}s" => nil_if_empty(@values[true]),
+            :"_negative_#{key}s" => nil_if_empty(@values[false])
           }
         end
         
         private
         
-        def add_value(value, is_positive)
-          if @values[!is_positive].include?(value)
-            raise Item::Search::Contradiction,
-                  "positive #{key} and negative #{key} both contain #{value}"
-          end
-          
-          @values[is_positive] << value
-        end
-        
         def nil_if_empty(set)
-          set unless set.empty?
+          set.map { |value| {key => value} } unless set.empty?
         end
       end
     end