diff --git a/lib/multi_xml.rb b/lib/multi_xml.rb
index ad97a75..062a7de 100644
--- a/lib/multi_xml.rb
+++ b/lib/multi_xml.rb
@@ -57,7 +57,7 @@ class ParseError < StandardError; end
   class << self
     # Get the current parser class.
     def parser
-      return @@parser if defined?(@@parser)
+      return @@parser unless @@parser.nil?
       self.parser = self.default_parser
       @@parser
     end
diff --git a/spec/multi_xml_spec.rb b/spec/multi_xml_spec.rb
index 782325c..195bdc1 100644
--- a/spec/multi_xml_spec.rb
+++ b/spec/multi_xml_spec.rb
@@ -5,6 +5,10 @@ class MockDecoder; end
 
 describe "MultiXml" do
   context "Parsers" do
+    before do
+      MultiXml.send :class_variable_set, :@@parser, nil
+    end
+
     it "should pick a default parser" do
       MultiXml.parser.should be_kind_of(Module)
       MultiXml.parser.should respond_to(:parse)