diff --git a/Gemfile.lock b/Gemfile.lock
index 301191c..3e298ab 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -1,7 +1,7 @@
 PATH
   remote: .
   specs:
-    decanter (4.0.4)
+    decanter (4.1.0)
       actionpack (>= 4.2.10)
       activesupport
       rails-html-sanitizer (>= 1.0.4)
diff --git a/README.md b/README.md
index 8ebd332..82ae997 100644
--- a/README.md
+++ b/README.md
@@ -185,6 +185,12 @@ input :start_date, :date, parse_format: '%Y-%m-%d'
 | `DateParser`| `parse_format` | `'%m/%d/%Y'`| Accepts any format string accepted by Ruby's `strftime` method
 | `DateTimeParser` | `parse_format` | `'%m/%d/%Y %I:%M:%S %p'` | Accepts any format string accepted by Ruby's `strftime` method
 
+`:boolean` will parse values of `true` and `1` as truthy. If another value is expected to be truthy, use the option `truth_value` to assign a custom truthy case.
+
+```ruby
+input :checkbox, :boolean, truth_value: 'yes'
+```
+
 ### Exceptions
 
 By default, `Decanter#decant` will raise an exception when unexpected parameters are passed. To override this behavior, you can change the strict mode option to one of:
diff --git a/lib/decanter/parser/boolean_parser.rb b/lib/decanter/parser/boolean_parser.rb
index 5ac6ca4..0c8bd65 100644
--- a/lib/decanter/parser/boolean_parser.rb
+++ b/lib/decanter/parser/boolean_parser.rb
@@ -5,6 +5,19 @@ class BooleanParser < ValueParser
       allow TrueClass, FalseClass
 
       parser do |val, options|
+        normalized_val = normalize(val)
+        next if normalized_val.nil?
+
+        true_values = ['1', 'true']
+
+        option_val = options.fetch(:true_value, nil)
+        normalized_option = normalize(option_val)
+
+        true_values << normalized_option if normalized_option
+        true_values.find {|tv| !!/#{tv}/i.match(normalized_val)}.present?
+      end
+
+      def self.normalize(value)
         raise Decanter::ParseError.new 'Expects a single value' if val.is_a? Array
         next if (val.nil? || val === '')
         [1, '1'].include?(val) || !!/^true$/i.match?(val.to_s)
diff --git a/lib/decanter/version.rb b/lib/decanter/version.rb
index 09aa6a1..41bd3a3 100644
--- a/lib/decanter/version.rb
+++ b/lib/decanter/version.rb
@@ -1,3 +1,3 @@
 module Decanter
-  VERSION = '4.0.4'.freeze
+  VERSION = '4.1.0'.freeze
 end
diff --git a/spec/decanter/parser/boolean_parser_spec.rb b/spec/decanter/parser/boolean_parser_spec.rb
index 3f0493c..f950c3b 100644
--- a/spec/decanter/parser/boolean_parser_spec.rb
+++ b/spec/decanter/parser/boolean_parser_spec.rb
@@ -12,7 +12,6 @@
       ['boolean', true],
       ['string', 'true'],
       ['string', 'True'],
-      ['string', 'truE']
     ]
 
     falses = [
@@ -20,8 +19,22 @@
       ['number', 2],
       ['string', '2'],
       ['boolean', false],
-      ['string', 'tru'],
-      ['string', 'not true']
+    ]
+
+    trues_with_options = [
+      ['string', 'yes', 'string', 'yes'],
+      ['string', 'Yes', 'string', 'yes'],
+      ['string', 'is true', 'string', 'is true'],
+      ['string', 'is truE', 'string', 'is True'],
+      ['number', 3, 'number', 3],
+      ['number', 3, 'string', '3'],
+      ['string', '3', 'number', 3],
+      ['string', 'false', 'string', 'false'],
+      ['string', 'false', 'string', 'False'],
+    ]
+
+    falses_with_options = [
+      ['string', 'yes', 'string', '']
     ]
 
     let(:name) { :foo }
@@ -62,5 +75,33 @@
           .to raise_error(Decanter::ParseError)
       end
     end
+
+    context 'returns true with options for' do
+      trues_with_options.each do |cond|
+        it "#{cond[0]}: #{cond[1]}, option: {#{cond[2]}: #{cond[3]}}" do
+          expect(parser.parse(name, cond[1], true_value: cond[3])).to match({name => true})
+        end
+      end
+    end
+
+    context 'returns false with options for' do
+      falses_with_options.each do |cond|
+        it "#{cond[0]}: #{cond[1]}, option: {#{cond[2]}: #{cond[3]}}" do
+          expect(parser.parse(name, cond[1], true_value: cond[3])).to match({name => false})
+        end
+      end
+    end
+
+    context 'with empty string and empty options' do
+      it 'returns nil' do
+        expect(parser.parse(name, '', true_value: '')).to match({name => nil})
+      end
+    end
+
+    context 'with nil and nil options' do
+      it 'returns nil' do
+        expect(parser.parse(name, nil, true_value: nil)).to match({name => nil})
+      end
+    end
   end
 end