diff --git a/lib/interactor.rb b/lib/interactor.rb
index 2423630..6e0babd 100644
--- a/lib/interactor.rb
+++ b/lib/interactor.rb
@@ -75,6 +75,14 @@ def call(context = {})
     def call!(context = {})
       new(context).tap(&:run!).context
     end
+
+    def context_class
+      @context_class || Interactor::Context
+    end
+
+    def context_class=(klass)
+      @context_class = klass
+    end
   end
 
   # Internal: Initialize an Interactor.
@@ -91,7 +99,7 @@ def call!(context = {})
   #   MyInteractor.new
   #   # => #<MyInteractor @context=#<Interactor::Context>>
   def initialize(context = {})
-    @context = Context.build(context)
+    @context = self.class.context_class.build(context)
   end
 
   # Internal: Invoke an interactor instance along with all defined hooks. The
diff --git a/lib/interactor/context.rb b/lib/interactor/context.rb
index cb269d2..0d4c8f0 100644
--- a/lib/interactor/context.rb
+++ b/lib/interactor/context.rb
@@ -29,153 +29,173 @@ module Interactor
   #   context
   #   # => #<Interactor::Context foo="baz" hello="world">
   class Context < OpenStruct
-    # Internal: Initialize an Interactor::Context or preserve an existing one.
-    # If the argument given is an Interactor::Context, the argument is returned.
-    # Otherwise, a new Interactor::Context is initialized from the provided
-    # hash.
-    #
-    # The "build" method is used during interactor initialization.
-    #
-    # context - A Hash whose key/value pairs are used in initializing a new
-    #           Interactor::Context object. If an existing Interactor::Context
-    #           is given, it is simply returned. (default: {})
-    #
-    # Examples
-    #
-    #   context = Interactor::Context.build(foo: "bar")
-    #   # => #<Interactor::Context foo="bar">
-    #   context.object_id
-    #   # => 2170969340
-    #   context = Interactor::Context.build(context)
-    #   # => #<Interactor::Context foo="bar">
-    #   context.object_id
-    #   # => 2170969340
-    #
-    # Returns the Interactor::Context.
-    def self.build(context = {})
-      context.is_a?(Context) ? context : new(context)
-    end
+    # Public: The default mixin any Context implementation should use
+    module Mixin
+      def self.included(receiver)
+        receiver.extend         ClassMethods
+        receiver.send :include, InstanceMethods
+      end
 
-    # Public: Whether the Interactor::Context is successful. By default, a new
-    # context is successful and only changes when explicitly failed.
-    #
-    # The "success?" method is the inverse of the "failure?" method.
-    #
-    # Examples
-    #
-    #   context = Interactor::Context.new
-    #   # => #<Interactor::Context>
-    #   context.success?
-    #   # => true
-    #   context.fail!
-    #   # => Interactor::Failure: #<Interactor::Context>
-    #   context.success?
-    #   # => false
-    #
-    # Returns true by default or false if failed.
-    def success?
-      !failure?
-    end
+      # Internal: Context class methods.
+      module ClassMethods
+        # Internal: Initialize an Interactor::Context or preserve an existing
+        # one.
+        # If the argument given is an Interactor::Context, the argument is
+        # returned. Otherwise, a new Interactor::Context is initialized from
+        # the provided hash.
+        #
+        # The "build" method is used during interactor initialization.
+        #
+        # context - A Hash whose key/value pairs are used in initializing a new
+        #           Interactor::Context object. If an existing
+        #           Interactor::Context is given, it is simply returned.
+        #           (default: {})
+        #
+        # Examples
+        #
+        #   context = Interactor::Context.build(foo: "bar")
+        #   # => #<Interactor::Context foo="bar">
+        #   context.object_id
+        #   # => 2170969340
+        #   context = Interactor::Context.build(context)
+        #   # => #<Interactor::Context foo="bar">
+        #   context.object_id
+        #   # => 2170969340
+        #
+        # Returns the Interactor::Context.
+        def build(context = {})
+          context.is_a?(self) ? context : new(context)
+        end
+      end
 
-    # Public: Whether the Interactor::Context has failed. By default, a new
-    # context is successful and only changes when explicitly failed.
-    #
-    # The "failure?" method is the inverse of the "success?" method.
-    #
-    # Examples
-    #
-    #   context = Interactor::Context.new
-    #   # => #<Interactor::Context>
-    #   context.failure?
-    #   # => false
-    #   context.fail!
-    #   # => Interactor::Failure: #<Interactor::Context>
-    #   context.failure?
-    #   # => true
-    #
-    # Returns false by default or true if failed.
-    def failure?
-      @failure || false
-    end
+      # Internal: Context instance methods.
+      module InstanceMethods
+        # Public: Whether the Interactor::Context is successful. By default, a
+        # new context is successful and only changes when explicitly failed.
+        #
+        # The "success?" method is the inverse of the "failure?" method.
+        #
+        # Examples
+        #
+        #   context = Interactor::Context.new
+        #   # => #<Interactor::Context>
+        #   context.success?
+        #   # => true
+        #   context.fail!
+        #   # => Interactor::Failure: #<Interactor::Context>
+        #   context.success?
+        #   # => false
+        #
+        # Returns true by default or false if failed.
+        def success?
+          !failure?
+        end
 
-    # Public: Fail the Interactor::Context. Failing a context raises an error
-    # that may be rescued by the calling interactor. The context is also flagged
-    # as having failed.
-    #
-    # Optionally the caller may provide a hash of key/value pairs to be merged
-    # into the context before failure.
-    #
-    # context - A Hash whose key/value pairs are merged into the existing
-    #           Interactor::Context instance. (default: {})
-    #
-    # Examples
-    #
-    #   context = Interactor::Context.new
-    #   # => #<Interactor::Context>
-    #   context.fail!
-    #   # => Interactor::Failure: #<Interactor::Context>
-    #   context.fail! rescue false
-    #   # => false
-    #   context.fail!(foo: "baz")
-    #   # => Interactor::Failure: #<Interactor::Context foo="baz">
-    #
-    # Raises Interactor::Failure initialized with the Interactor::Context.
-    def fail!(context = {})
-      context.each { |key, value| modifiable[key.to_sym] = value }
-      @failure = true
-      raise Failure, self
-    end
+        # Public: Whether the Interactor::Context has failed. By default, a new
+        # context is successful and only changes when explicitly failed.
+        #
+        # The "failure?" method is the inverse of the "success?" method.
+        #
+        # Examples
+        #
+        #   context = Interactor::Context.new
+        #   # => #<Interactor::Context>
+        #   context.failure?
+        #   # => false
+        #   context.fail!
+        #   # => Interactor::Failure: #<Interactor::Context>
+        #   context.failure?
+        #   # => true
+        #
+        # Returns false by default or true if failed.
+        def failure?
+          @failure || false
+        end
 
-    # Internal: Track that an Interactor has been called. The "called!" method
-    # is used by the interactor being invoked with this context. After an
-    # interactor is successfully called, the interactor instance is tracked in
-    # the context for the purpose of potential future rollback.
-    #
-    # interactor - An Interactor instance that has been successfully called.
-    #
-    # Returns nothing.
-    def called!(interactor)
-      _called << interactor
-    end
+        # Public: Fail the Interactor::Context. Failing a context raises an
+        # error that may be rescued by the calling interactor. The context is
+        # also flagged as having failed.
+        #
+        # Optionally the caller may provide a hash of key/value pairs to be
+        # merged into the context before failure.
+        #
+        # context - A Hash whose key/value pairs are merged into the existing
+        #           Interactor::Context instance. (default: {})
+        #
+        # Examples
+        #
+        #   context = Interactor::Context.new
+        #   # => #<Interactor::Context>
+        #   context.fail!
+        #   # => Interactor::Failure: #<Interactor::Context>
+        #   context.fail! rescue false
+        #   # => false
+        #   context.fail!(foo: "baz")
+        #   # => Interactor::Failure: #<Interactor::Context foo="baz">
+        #
+        # Raises Interactor::Failure initialized with the Interactor::Context.
+        def fail!(context = {})
+          context.each { |key, value| send("#{key}=", value) }
+          @failure = true
+          raise Failure, self
+        end
 
-    # Public: Roll back the Interactor::Context. Any interactors to which this
-    # context has been passed and which have been successfully called are asked
-    # to roll themselves back by invoking their "rollback" instance methods.
-    #
-    # Examples
-    #
-    #   context = MyInteractor.call(foo: "bar")
-    #   # => #<Interactor::Context foo="baz">
-    #   context.rollback!
-    #   # => true
-    #   context
-    #   # => #<Interactor::Context foo="bar">
-    #
-    # Returns true if rolled back successfully or false if already rolled back.
-    def rollback!
-      return false if @rolled_back
-      _called.reverse_each(&:rollback)
-      @rolled_back = true
-    end
+        # Internal: Track that an Interactor has been called. The "called!"
+        # method is used by the interactor being invoked with this context.
+        # After an interactor is successfully called, the interactor instance is
+        # tracked in the context for the purpose of potential future rollback.
+        #
+        # interactor - An Interactor instance that has been successfully called.
+        #
+        # Returns nothing.
+        def called!(interactor)
+          _called << interactor
+        end
 
-    # Internal: An Array of successfully called Interactor instances invoked
-    # against this Interactor::Context instance.
-    #
-    # Examples
-    #
-    #   context = Interactor::Context.new
-    #   # => #<Interactor::Context>
-    #   context._called
-    #   # => []
-    #
-    #   context = MyInteractor.call(foo: "bar")
-    #   # => #<Interactor::Context foo="baz">
-    #   context._called
-    #   # => [#<MyInteractor @context=#<Interactor::Context foo="baz">>]
-    #
-    # Returns an Array of Interactor instances or an empty Array.
-    def _called
-      @called ||= []
+        # Public: Roll back the Interactor::Context. Any interactors to which
+        # this context has been passed and which have been successfully called
+        # are asked to roll themselves back by invoking their "rollback"
+        # instance methods.
+        #
+        # Examples
+        #
+        #   context = MyInteractor.call(foo: "bar")
+        #   # => #<Interactor::Context foo="baz">
+        #   context.rollback!
+        #   # => true
+        #   context
+        #   # => #<Interactor::Context foo="bar">
+        #
+        # Returns true if rolled back successfully or false if already rolled
+        # back.
+        def rollback!
+          return false if @rolled_back
+          _called.reverse_each(&:rollback)
+          @rolled_back = true
+        end
+
+        # Internal: An Array of successfully called Interactor instances invoked
+        # against this Interactor::Context instance.
+        #
+        # Examples
+        #
+        #   context = Interactor::Context.new
+        #   # => #<Interactor::Context>
+        #   context._called
+        #   # => []
+        #
+        #   context = MyInteractor.call(foo: "bar")
+        #   # => #<Interactor::Context foo="baz">
+        #   context._called
+        #   # => [#<MyInteractor @context=#<Interactor::Context foo="baz">>]
+        #
+        # Returns an Array of Interactor instances or an empty Array.
+        def _called
+          @called ||= []
+        end
+      end
     end
+
+    include Mixin
   end
 end
diff --git a/spec/interactor/context_spec.rb b/spec/interactor/context_spec.rb
index eb8b905..37c659e 100644
--- a/spec/interactor/context_spec.rb
+++ b/spec/interactor/context_spec.rb
@@ -1,25 +1,18 @@
 module Interactor
-  describe Context do
+  shared_examples "context" do
     describe ".build" do
       it "converts the given hash to a context" do
-        context = Context.build(foo: "bar")
+        context = context_class.build(foo: "bar")
 
-        expect(context).to be_a(Context)
+        expect(context).to be_a(context_class)
         expect(context.foo).to eq("bar")
       end
 
-      it "builds an empty context if no hash is given" do
-        context = Context.build
-
-        expect(context).to be_a(Context)
-        expect(context.send(:table)).to eq({})
-      end
-
       it "doesn't affect the original hash" do
         hash = { foo: "bar" }
-        context = Context.build(hash)
+        context = context_class.build(hash)
 
-        expect(context).to be_a(Context)
+        expect(context).to be_a(context_class)
         expect {
           context.foo = "baz"
         }.not_to change {
@@ -28,10 +21,10 @@ module Interactor
       end
 
       it "preserves an already built context" do
-        context1 = Context.build(foo: "bar")
-        context2 = Context.build(context1)
+        context1 = context_class.build(foo: "bar")
+        context2 = context_class.build(context1)
 
-        expect(context2).to be_a(Context)
+        expect(context2).to be_a(context_class)
         expect {
           context2.foo = "baz"
         }.to change {
@@ -41,7 +34,7 @@ module Interactor
     end
 
     describe "#success?" do
-      let(:context) { Context.build }
+      let(:context) { context_class.build }
 
       it "is true by default" do
         expect(context.success?).to eq(true)
@@ -49,7 +42,7 @@ module Interactor
     end
 
     describe "#failure?" do
-      let(:context) { Context.build }
+      let(:context) { context_class.build }
 
       it "is false by default" do
         expect(context.failure?).to eq(false)
@@ -57,7 +50,7 @@ module Interactor
     end
 
     describe "#fail!" do
-      let(:context) { Context.build(foo: "bar") }
+      let(:context) { context_class.build(foo: "bar") }
 
       it "sets success to false" do
         expect {
@@ -125,7 +118,7 @@ module Interactor
     end
 
     describe "#called!" do
-      let(:context) { Context.build }
+      let(:context) { context_class.build }
       let(:instance1) { double(:instance1) }
       let(:instance2) { double(:instance2) }
 
@@ -140,7 +133,7 @@ module Interactor
     end
 
     describe "#rollback!" do
-      let(:context) { Context.build }
+      let(:context) { context_class.build }
       let(:instance1) { double(:instance1) }
       let(:instance2) { double(:instance2) }
 
@@ -165,11 +158,51 @@ module Interactor
     end
 
     describe "#_called" do
-      let(:context) { Context.build }
+      let(:context) { context_class.build }
 
       it "is empty by default" do
         expect(context._called).to eq([])
       end
     end
   end
+
+  describe Context do
+    it_behaves_like "context" do
+      let(:context_class) { Context }
+
+      it "builds an empty context if no hash is given" do
+        context = context_class.build
+
+        expect(context).to be_a(context_class)
+        expect(context.send(:table)).to eq({})
+      end
+    end
+  end
+
+  describe "Overwriting Context" do
+    it_behaves_like "context" do
+      let(:context_class) do
+        Class.new do
+          include Context::Mixin
+
+          attr_accessor :foo
+
+          def initialize(foo: nil)
+            @foo = foo
+          end
+
+          def to_h
+            { foo: foo }
+          end
+        end
+      end
+
+      it "builds the default context if no hash is given" do
+        context = context_class.build
+
+        expect(context).to be_a(context_class)
+        expect(context.to_h).to eq(foo: nil)
+      end
+    end
+  end
 end