diff --git a/.gitignore b/.gitignore
index 9f30a35..673611c 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,4 @@
 pkg/*
 *.gem
 .bundle
+tmp/*.sqlite3
diff --git a/lib/generators/crono/install/templates/migrations/create_crono_jobs.rb b/lib/generators/crono/install/templates/migrations/create_crono_jobs.rb
index d714dae..476d295 100644
--- a/lib/generators/crono/install/templates/migrations/create_crono_jobs.rb
+++ b/lib/generators/crono/install/templates/migrations/create_crono_jobs.rb
@@ -4,7 +4,7 @@ class CreateCronoJobs < ActiveRecord::Migration
       t.string    :job_id, null: false
       t.text      :log
       t.datetime  :last_performed_at
-      t.timestamps
+      t.timestamps null: false
     end
     add_index :crono_jobs, [:job_id], unique: true
   end
diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
index e13ac03..d6d6342 100644
--- a/spec/spec_helper.rb
+++ b/spec/spec_helper.rb
@@ -1,3 +1,5 @@
+TMP_DB_FILE = "tmp/test_db.sqlite3"
+
 require 'bundler/setup'
 Bundler.setup
 
@@ -6,7 +8,9 @@ require 'byebug'
 require 'crono'
 require 'generators/crono/install/templates/migrations/create_crono_jobs.rb'
 
-ActiveRecord::Base.establish_connection(adapter: 'sqlite3', database: ':memory:')
+FileUtils.rm(TMP_DB_FILE) if File.exist?(TMP_DB_FILE)
+
+ActiveRecord::Base.establish_connection(adapter: 'sqlite3', database: TMP_DB_FILE)
 ActiveRecord::Base.logger = Logger.new(STDOUT)
 CreateCronoJobs.up
 
diff --git a/tmp/.gitkeep b/tmp/.gitkeep
new file mode 100644
index 0000000..e69de29