diff --git a/lib/database_cleaner/active_record/truncation.rb b/lib/database_cleaner/active_record/truncation.rb
index 78183e8..618d06e 100755
--- a/lib/database_cleaner/active_record/truncation.rb
+++ b/lib/database_cleaner/active_record/truncation.rb
@@ -172,9 +172,15 @@ module DatabaseCleaner
       # but then the table is cleaned.  In other words, this function tells us if the given table
       # was ever inserted into.
       def has_been_used?(table)
+        return has_rows?(table) unless has_sequence?(table)
+
         cur_val = select_value("SELECT currval('#{table}_id_seq');").to_i rescue 0
         cur_val > 0
       end
+      
+      def has_sequence?(table)
+        select_value("SELECT true FROM pg_class WHERE relname = '#{table}_id_seq';")
+      end
 
       def has_rows?(table)
         select_value("SELECT true FROM #{table} LIMIT 1;")
diff --git a/spec/database_cleaner/active_record/truncation/postgresql_spec.rb b/spec/database_cleaner/active_record/truncation/postgresql_spec.rb
index 6a479d0..8ad59fe 100644
--- a/spec/database_cleaner/active_record/truncation/postgresql_spec.rb
+++ b/spec/database_cleaner/active_record/truncation/postgresql_spec.rb
@@ -25,6 +25,13 @@ module ActiveRecord
           User.count.should eq 0
         end
 
+        it "truncates the table without id sequence" do
+          2.times { Agent.create }
+
+          connection.truncate_table('agents')
+          Agent.count.should eq 0
+        end
+
         it "resets AUTO_INCREMENT index of table" do
           2.times { User.create }
           User.delete_all
@@ -48,4 +55,3 @@ module ActiveRecord
     end
   end
 end
-
diff --git a/spec/support/active_record/schema_setup.rb b/spec/support/active_record/schema_setup.rb
index 39aacb4..59d62ac 100644
--- a/spec/support/active_record/schema_setup.rb
+++ b/spec/support/active_record/schema_setup.rb
@@ -3,8 +3,15 @@ def active_record_load_schema
     create_table :users, :force => true do |t|
       t.integer :name
     end
+
+    create_table :agents, :id => false, :force => true do |t|
+      t.integer :name
+    end
   end
 end
 
 class ::User < ActiveRecord::Base
 end
+
+class ::Agent < ActiveRecord::Base
+end