diff --git a/.drone.yml b/.drone.yml
index 4a253a9..279c99e 100644
--- a/.drone.yml
+++ b/.drone.yml
@@ -8,6 +8,7 @@ build:
     - /home/data/drone/key_cache:/ssh_keys
   environment:
     - COMPOSE_FILE_EXT=drone
+    - RUBY_IMAGE_TAG=2.2-latest
   commands:
     - wrapdocker docker -v
 
diff --git a/Appraisals b/Appraisals
index e17b0cb..624e33d 100644
--- a/Appraisals
+++ b/Appraisals
@@ -1,11 +1,9 @@
 appraise 'rails3.2' do
-  gem 'activerecord', '~> 3.2.0'
   gem 'actionpack', '~> 3.2.0'
   gem 'activesupport', '~> 3.2.0'
 end
 
 appraise 'rails4.0' do
-  gem 'activerecord', '~> 4.0.0'
   gem 'actionpack', '~> 4.0.0'
   gem 'activesupport', '~> 4.0.0'
 end
diff --git a/lib/string_tools/core_ext/string.rb b/lib/string_tools/core_ext/string.rb
index 9b1c956..bbef1a9 100644
--- a/lib/string_tools/core_ext/string.rb
+++ b/lib/string_tools/core_ext/string.rb
@@ -3,8 +3,9 @@
 require 'rchardet19'
 require 'addressable/uri'
 require 'active_support/core_ext/module'
-require 'active_record'
+require 'active_support/version'
 require 'action_pack'
+require 'string_tools/string'
 
 class String
   %w[auto_link excerpt highlight sanitize simple_format word_wrap].each do |method|
@@ -30,7 +31,7 @@ def to_f_with_strip_comma
   alias_method_chain :to_f, :strip_comma
 
   def to_b
-    ActiveRecord::ConnectionAdapters::Column.value_to_boolean(self) || false
+    StringTools::String.new(self).to_b
   end
 
   def to_script_safe_json
diff --git a/lib/string_tools/string.rb b/lib/string_tools/string.rb
new file mode 100644
index 0000000..25a8c4c
--- /dev/null
+++ b/lib/string_tools/string.rb
@@ -0,0 +1,20 @@
+module StringTools
+  class String
+    TRUE_VALUES = %w(1 t T true TRUE on ON).to_set
+
+    def initialize(string)
+      @string = string
+    end
+
+    # Public: cast string value to boolean
+    #
+    # Example:
+    #   StringTools::String.new('t').to_b
+    #   #=> true
+    #
+    # Return boolean
+    def to_b
+      TRUE_VALUES.include?(@string)
+    end
+  end
+end
diff --git a/spec/string_tools/string_spec.rb b/spec/string_tools/string_spec.rb
new file mode 100644
index 0000000..766be8b
--- /dev/null
+++ b/spec/string_tools/string_spec.rb
@@ -0,0 +1,15 @@
+require 'spec_helper'
+
+RSpec.describe StringTools::String, '#to_b' do
+  ["0", "f", "F", "false", "FALSE", "off", "OFF", "", "2017-01-01"].each do |val|
+    it "returns false" do
+      expect(described_class.new(val).to_b).to be false
+    end
+  end
+
+  %w(1 t T true TRUE on ON).each do |val|
+    it "returns true" do
+      expect(described_class.new(val).to_b).to be true
+    end
+  end
+end
diff --git a/string_tools.gemspec b/string_tools.gemspec
index 28bd364..dea96f8 100644
--- a/string_tools.gemspec
+++ b/string_tools.gemspec
@@ -19,7 +19,6 @@ Gem::Specification.new do |spec|
   spec.test_files    = spec.files.grep(%r{^(test|spec|features)/})
   spec.require_paths = ['lib']
 
-  spec.add_runtime_dependency 'activerecord', '>= 3.1.12'
   spec.add_runtime_dependency 'actionpack', '>= 3.1.12'
   spec.add_runtime_dependency 'activesupport', '>= 3.1.12'
   spec.add_runtime_dependency 'rchardet19', '~> 1.3.5'