diff --git a/Gemfile b/Gemfile
index 903d37f..6db22ce 100644
--- a/Gemfile
+++ b/Gemfile
@@ -6,4 +6,6 @@ group :development, :test do
   gem 'combustion', github: 'pat/combustion', ref: '7d0d24c3f36ce0eb336177fc493be0721bc26665'
 end
 
+gem 'rack', '< 2' if RUBY_VERSION < '2.2.0'
+
 gemspec
diff --git a/lib/redis_counters/dumpers/engine.rb b/lib/redis_counters/dumpers/engine.rb
index 3f54c6c..f78a310 100644
--- a/lib/redis_counters/dumpers/engine.rb
+++ b/lib/redis_counters/dumpers/engine.rb
@@ -272,7 +272,11 @@ def columns_definition
                           when :boolean
                             'boolean'
                           else
-                            raise 'Unknown datatype %s for %s field' % [type, field]
+                            if type.is_a?(Array) && type.first == :enum
+                              type.last.fetch(:name)
+                            else
+                              raise 'Unknown datatype %s for %s field' % [type, field]
+                            end
                           end
 
           "#{field} #{pg_field_type}"
diff --git a/redis_counters-dumpers.gemspec b/redis_counters-dumpers.gemspec
index 22ca275..4b0ad7a 100644
--- a/redis_counters-dumpers.gemspec
+++ b/redis_counters-dumpers.gemspec
@@ -25,7 +25,6 @@ Gem::Specification.new do |spec|
   spec.add_dependency 'callbacks_rb', '>= 0.0.1'
   spec.add_dependency 'redis_counters', '>= 1.3'
 
-
   spec.add_development_dependency 'bundler', '>= 1.7'
   spec.add_development_dependency 'rake', '>= 10.0'
   spec.add_development_dependency 'rspec', '>= 3.2'
diff --git a/spec/internal/db/schema.rb b/spec/internal/db/schema.rb
index 90f408c..47a7b55 100644
--- a/spec/internal/db/schema.rb
+++ b/spec/internal/db/schema.rb
@@ -1,9 +1,14 @@
 ActiveRecord::Schema.define do
+  execute <<-SQL
+    CREATE TYPE subject_types AS ENUM ('');
+  SQL
+
   create_table :stats_by_days do |t|
     t.integer :record_id, null: false
     t.integer :column_id, null: false
     t.date :date, null: false
     t.integer :hits, null: false, default: 0
+    t.column :subject, :subject_types
   end
 
   add_index :stats_by_days, [:record_id, :column_id, :date], unique: true
@@ -12,6 +17,7 @@
     t.integer :record_id, null: false
     t.integer :column_id, null: false
     t.integer :hits, null: false, default: 0
+    t.column :subject, :subject_types
   end
 
   add_index :stats_totals, [:record_id, :column_id], unique: true
@@ -19,6 +25,7 @@
   create_table :stats_agg_totals do |t|
     t.integer :record_id, null: false
     t.integer :hits, null: false, default: 0
+    t.column :subject, :subject_types
   end
 
   add_index :stats_agg_totals, [:record_id], unique: true
diff --git a/spec/lib/redis_counters/dumpers/engine_spec.rb b/spec/lib/redis_counters/dumpers/engine_spec.rb
index 6ee43bf..681c6f5 100644
--- a/spec/lib/redis_counters/dumpers/engine_spec.rb
+++ b/spec/lib/redis_counters/dumpers/engine_spec.rb
@@ -7,7 +7,8 @@
       fields record_id: :integer,
              column_id: :integer,
              value: :integer,
-             date: :date
+             date: :date,
+             subject: [:enum, {name: :subject_types}]
 
       destination do
         model StatsByDay
@@ -51,7 +52,7 @@
     RedisCounters.create_counter(Redis.current,
       counter_class: RedisCounters::HashCounter,
       counter_name: :record_hits_by_day,
-      group_keys: [:record_id, :column_id],
+      group_keys: [:record_id, :column_id, :subject],
       partition_keys: [:date]
     )
   end
@@ -62,17 +63,17 @@
 
   describe '#process!' do
     before do
-      counter.increment(date: prev_date_s, record_id: 1, column_id: 100)
-      counter.increment(date: prev_date_s, record_id: 1, column_id: 200)
-      counter.increment(date: prev_date_s, record_id: 1, column_id: 200)
-      counter.increment(date: prev_date_s, record_id: 2, column_id: 100)
+      counter.increment(date: prev_date_s, record_id: 1, column_id: 100, subject: '')
+      counter.increment(date: prev_date_s, record_id: 1, column_id: 200, subject: '')
+      counter.increment(date: prev_date_s, record_id: 1, column_id: 200, subject: '')
+      counter.increment(date: prev_date_s, record_id: 2, column_id: 100, subject: nil)
 
       dumper.process!(counter, prev_date)
 
-      counter.increment(date: date_s, record_id: 1, column_id: 100)
-      counter.increment(date: date_s, record_id: 1, column_id: 200)
-      counter.increment(date: date_s, record_id: 1, column_id: 200)
-      counter.increment(date: date_s, record_id: 2, column_id: 100)
+      counter.increment(date: date_s, record_id: 1, column_id: 100, subject: '')
+      counter.increment(date: date_s, record_id: 1, column_id: 200, subject: '')
+      counter.increment(date: date_s, record_id: 1, column_id: 200, subject: '')
+      counter.increment(date: date_s, record_id: 2, column_id: 100, subject: nil)
 
       dumper.process!(counter, date)
     end