diff --git a/lib/omniauth/strategies/cas/logout_request.rb b/lib/omniauth/strategies/cas/logout_request.rb
index eba676c..9fa1654 100644
--- a/lib/omniauth/strategies/cas/logout_request.rb
+++ b/lib/omniauth/strategies/cas/logout_request.rb
@@ -31,22 +31,18 @@ def call(options = {})
         def logout_request
           @logout_request ||= begin
             saml = Nokogiri.parse(@request.params['logoutRequest'])
-            name_id = saml.xpath('//saml:NameID').text
-            sess_idx = saml.xpath('//samlp:SessionIndex').text
+            ns = saml.collect_namespaces
+            name_id = saml.xpath('//saml:NameID', ns).text
+            sess_idx = saml.xpath('//samlp:SessionIndex', ns).text
             inject_params(name_id:name_id, session_index:sess_idx)
             @request
           end
         end
 
         def inject_params(new_params)
-          rack_input = @request.env['rack.input'].read
-          params = Rack::Utils.parse_query(rack_input, '&').merge new_params
-          @request.env['rack.input'] = StringIO.new(Rack::Utils.build_query(params))
-        rescue
-          # A no-op intended to ensure that the ensure block is run
-          raise
-        ensure
-          @request.env['rack.input'].rewind
+          new_params.each do |k,v|
+            @request.update_param(k,v)
+          end
         end
 
         def single_sign_out_callback