diff --git a/Changelog.md b/Changelog.md
index 74b73e86c..a24d4dc83 100644
--- a/Changelog.md
+++ b/Changelog.md
@@ -18,6 +18,9 @@ Bug Fixes:
   `and_yield`, `and_raise`, `and_return` or `and_throw`. This got fixed
   in 2.13.1 but failed to get merged into master for the 2.14.0.rc1
   release (Myron Marston).
+* `Marshal.dump` does not unnecessarily duplicate objects when rspec-mocks has
+  not been fully initialized. This could cause errors when using `spork` or
+  similar preloading gems (Andy Lindeman).
 
 ### 2.14.0.rc1 / 2013-05-27
 [full changelog](http://github.com/rspec/rspec-mocks/compare/v2.13.0...v2.14.0.rc1)
diff --git a/lib/rspec/mocks/extensions/marshal.rb b/lib/rspec/mocks/extensions/marshal.rb
index 7698c1887..b8cf7b5df 100644
--- a/lib/rspec/mocks/extensions/marshal.rb
+++ b/lib/rspec/mocks/extensions/marshal.rb
@@ -1,13 +1,13 @@
 module Marshal
   class << self
-    def dump_with_mocks(*args)
-      object = args.shift
-
-      if ( ::RSpec::Mocks.space && !::RSpec::Mocks.space.registered?(object) ) || NilClass === object
-        return dump_without_mocks(*args.unshift(object))
+    # Duplicates any mock objects before serialization. Otherwise,
+    # serialization will fail because methods exist on the singleton class.
+    def dump_with_mocks(object, *rest)
+      if ::RSpec::Mocks.space.nil? || !::RSpec::Mocks.space.registered?(object) || NilClass === object
+        dump_without_mocks(object, *rest)
+      else
+        dump_without_mocks(object.dup, *rest)
       end
-
-      dump_without_mocks(*args.unshift(object.dup))
     end
 
     alias_method :dump_without_mocks, :dump
diff --git a/spec/rspec/mocks/extensions/marshal_spec.rb b/spec/rspec/mocks/extensions/marshal_spec.rb
new file mode 100644
index 000000000..46f436b34
--- /dev/null
+++ b/spec/rspec/mocks/extensions/marshal_spec.rb
@@ -0,0 +1,54 @@
+require 'spec_helper'
+
+describe Marshal, 'extensions' do
+  # An object that raises when code attempts to dup it.
+  #
+  # Because we manipulate the internals of RSpec::Mocks.space below, we need
+  # an object that simply blows up when #dup is called without using any
+  # partial mocking or stubbing from rspec-mocks itself.
+  class UndupableObject
+    def dup
+      raise NotImplementedError
+    end
+  end
+
+  describe '#dump' do
+    context 'when rspec-mocks has not been fully initialized' do
+      def without_space
+        stashed_space, RSpec::Mocks.space = RSpec::Mocks.space, nil
+        yield
+      ensure
+        RSpec::Mocks.space = stashed_space
+      end
+
+      it 'does not duplicate the object before serialization' do
+        obj = UndupableObject.new
+        without_space do
+          serialized = Marshal.dump(obj)
+          expect(Marshal.load(serialized)).to be_an(UndupableObject)
+        end
+      end
+    end
+
+    context 'when rspec-mocks has been fully initialized' do
+      it 'duplicates objects with stubbed or mocked implementations before serialization' do
+        obj = double(:foo => "bar")
+
+        serialized = Marshal.dump(obj)
+        expect(Marshal.load(serialized)).to be_an(obj.class)
+      end
+
+      it 'does not duplicate other objects before serialization' do
+        obj = UndupableObject.new
+
+        serialized = Marshal.dump(obj)
+        expect(Marshal.load(serialized)).to be_an(UndupableObject)
+      end
+
+      it 'does not duplicate nil before serialization' do
+        serialized = Marshal.dump(nil)
+        expect(Marshal.load(serialized)).to be_nil
+      end
+    end
+  end
+end