diff --git a/spec/database_cleaner/data_mapper/truncation/sqlite3_spec.rb b/spec/database_cleaner/data_mapper/truncation/sqlite3_spec.rb
index d163ce9..90fa3e4 100644
--- a/spec/database_cleaner/data_mapper/truncation/sqlite3_spec.rb
+++ b/spec/database_cleaner/data_mapper/truncation/sqlite3_spec.rb
@@ -14,18 +14,18 @@ RSpec.describe DatabaseCleaner::DataMapper::Truncation do
 
   describe "DM connection adapter monkeypatches" do
     before do
-      2.times { DmUser.create }
+      2.times { User.create }
     end
 
     describe "#truncate_table" do
       it "truncates the table" do
-        connection.truncate_table(DmUser.storage_names[:default])
-        expect(DmUser.count).to eq 0
+        connection.truncate_table(User.storage_names[:default])
+        expect(User.count).to eq 0
       end
 
       it "resets AUTO_INCREMENT index of table" do
-        connection.truncate_table(DmUser.storage_names[:default])
-        expect(DmUser.create.id).to eq 1
+        connection.truncate_table(User.storage_names[:default])
+        expect(User.create.id).to eq 1
       end
     end
   end
diff --git a/spec/support/data_mapper/sqlite3_helper.rb b/spec/support/data_mapper/sqlite3_helper.rb
index 46279cb..762285f 100644
--- a/spec/support/data_mapper/sqlite3_helper.rb
+++ b/spec/support/data_mapper/sqlite3_helper.rb
@@ -2,18 +2,27 @@ require 'dm-core'
 require 'dm-sqlite-adapter'
 require 'support/database_helper'
 
-class ::DmUser
-  include DataMapper::Resource
-
-  self.storage_names[:default] = 'users'
-
-  property :id, Serial
-  property :name, String
-end
-
 class DataMapperSQLite3Helper < DatabaseHelper
   puts "DataMapper #{DataMapper::VERSION}, sqlite3"
 
+  def setup
+    Kernel.const_set "User", Class.new
+    User.instance_eval do
+      include DataMapper::Resource
+
+      storage_names[:default] = 'users'
+
+      property :id, User::Serial
+      property :name, String
+    end
+
+    super
+  end
+
+  def teardown
+    Kernel.send :remove_const, "User" if defined?(User)
+  end
+
   def connection
     DataMapper.repository.adapter
   end