diff --git a/lib/droonga/catalog/slices.rb b/lib/droonga/catalog/slices.rb
index 93ae39a3..8a7dbac2 100644
--- a/lib/droonga/catalog/slices.rb
+++ b/lib/droonga/catalog/slices.rb
@@ -39,9 +39,7 @@ def slicer
 
       def slices
         return nil unless @data.key?("slices")
-        @slices ||= @data["slices"].collect do |raw_slice|
-          Slice.new(@dataset, raw_slice)
-        end
+        @slices ||= create_slices
       end
 
       def select_slices(range=0..-1)
@@ -109,6 +107,12 @@ def stringify_key(key)
         end
       end
 
+      def create_slices
+        @data["slices"].collect do |raw_slice|
+          Slice.new(@dataset, raw_slice)
+        end
+      end
+
       def collect_all_nodes
         nodes = []
         slices.each do |slice|