diff --git a/Changelog.md b/Changelog.md
index 2c39be1e..269915c6 100644
--- a/Changelog.md
+++ b/Changelog.md
@@ -1,5 +1,6 @@
 # v0.2.4 2012-12-08
 
+* [feature] define block arguments
 * [feature] Mutate block arguments, inklusive pattern args
 * [feature] Recurse into block bodies
 * [fixed] Crash on mutating yield, added a noop for now
diff --git a/lib/mutant/mutator/node/define.rb b/lib/mutant/mutator/node/define.rb
index 65e2f6c8..f02b3b00 100644
--- a/lib/mutant/mutator/node/define.rb
+++ b/lib/mutant/mutator/node/define.rb
@@ -4,9 +4,26 @@ module Mutant
       class Define < self
 
         handle(Rubinius::AST::Define)
-        handle(Rubinius::AST::DefineSingleton)
         handle(Rubinius::AST::DefineSingletonScope)
 
+      private
+
+        # Emit mutations
+        #
+        # @return [undefined]
+        #
+        # @api private
+        #
+        def dispatch
+          emit_attribute_mutations(:body)
+          emit_attribute_mutations(:arguments)
+        end
+      end
+
+      class DefineSingleton < self
+
+        handle(Rubinius::AST::DefineSingleton)
+
       private
 
         # Emit mutations
diff --git a/spec/unit/mutant/mutator/node/define/mutation_spec.rb b/spec/unit/mutant/mutator/node/define/mutation_spec.rb
index 84b5aa41..a32ba58d 100644
--- a/spec/unit/mutant/mutator/node/define/mutation_spec.rb
+++ b/spec/unit/mutant/mutator/node/define/mutation_spec.rb
@@ -23,6 +23,35 @@ describe Mutant::Mutator, 'define' do
     it_should_behave_like 'a mutator'
   end
 
+  context 'with arguments' do
+    let(:source) { 'def foo(a, b); nil; end' }
+
+    before do
+      Mutant::Random.stub(:hex_string => 'random')
+    end
+
+    let(:mutations) do
+      mutations = []
+
+      # Deletion of each argument
+      mutations << 'def foo(a); nil; end'
+      mutations << 'def foo(b); nil; end'
+
+      # Deletion of all arguments
+      mutations << 'def foo; nil; end'
+
+      # Rename each argument
+      mutations << 'def foo(srandom, b); nil; end'
+      mutations << 'def foo(a, srandom); nil; end'
+
+      # Mutation of body
+      mutations << 'def foo(a, b); Object.new; end'
+    end
+
+
+    it_should_behave_like 'a mutator'
+  end
+
   context 'define on singleton' do
     let(:source) { 'def self.foo; self.bar; self.baz; end' }
 
@@ -44,4 +73,32 @@ describe Mutant::Mutator, 'define' do
     it_should_behave_like 'a mutator'
   end
 
+  context 'define on singleton with argument' do
+
+    before do
+      Mutant::Random.stub(:hex_string => 'random')
+    end
+
+    let(:source) { 'def self.foo(a, b); nil; end' }
+
+    let(:mutations) do
+      mutations = []
+
+      # Deletion of each argument
+      mutations << 'def self.foo(a); nil; end'
+      mutations << 'def self.foo(b); nil; end'
+
+      # Deletion of all arguments
+      mutations << 'def self.foo; nil; end'
+
+      # Rename each argument
+      mutations << 'def self.foo(srandom, b); nil; end'
+      mutations << 'def self.foo(a, srandom); nil; end'
+
+      # Mutation of body
+      mutations << 'def self.foo(a, b); Object.new; end'
+    end
+
+    it_should_behave_like 'a mutator'
+  end
 end