diff --git a/lib/capybara/driver/node.rb b/lib/capybara/driver/node.rb
index 330b0e6e..41b9f8d5 100644
--- a/lib/capybara/driver/node.rb
+++ b/lib/capybara/driver/node.rb
@@ -20,6 +20,7 @@ module Capybara
         raise NotImplementedError
       end
 
+      # @param value String or Array. Array is only allowed if node has 'multiple' attribute
       def set(value)
         raise NotImplementedError
       end
diff --git a/lib/capybara/node/actions.rb b/lib/capybara/node/actions.rb
index 6ce907f0..35dec47d 100644
--- a/lib/capybara/node/actions.rb
+++ b/lib/capybara/node/actions.rb
@@ -153,12 +153,11 @@ module Capybara
       # @param [String] path          The path of the file that will be attached, or an array of paths
       #
       def attach_file(locator, path)
-        path = [path] if String === path
-        path.each do |p|
+        (String === path ? [path] : path).each do |p|
           raise Capybara::FileNotFound, "cannot attach file, #{p} does not exist" unless File.exist?(p.to_s)
         end
         msg = "cannot attach file, no file field with id, name, or label '#{locator}' found"
-        find(:xpath, XPath::HTML.file_field(locator), :message => msg).set(path.to_yaml)
+        find(:xpath, XPath::HTML.file_field(locator), :message => msg).set(path)
       end
     end
   end
diff --git a/lib/capybara/rack_test/form.rb b/lib/capybara/rack_test/form.rb
index 765cc7ef..ecd02f6f 100644
--- a/lib/capybara/rack_test/form.rb
+++ b/lib/capybara/rack_test/form.rb
@@ -26,30 +26,17 @@ class Capybara::RackTest::Form < Capybara::RackTest::Node
           # TO DO identify the click button here (in document order, rather
           # than leaving until the end of the params)
         elsif field['type'] =='file'
-          value = field['value']
-          path_names = value.to_s.empty? ? [] : YAML::load(value.to_s)
           if multipart?
-            files = \
-              if path_names.empty?
-                [NilUploadedFile.new]
+            file = \
+              if (value = field['value']).to_s.empty?
+                NilUploadedFile.new
               else
-                if field['multiple']
-                  path_names.map do |path_name|
-                    content_type = MIME::Types.type_for(path_name).first.to_s
-                    Rack::Test::UploadedFile.new(path_name, content_type)
-                  end
-                else
-                  content_type = MIME::Types.type_for(path_names.last).first.to_s
-                  [Rack::Test::UploadedFile.new(path_names.last, content_type)]
-                end
+                content_type = MIME::Types.type_for(value).first.to_s
+                Rack::Test::UploadedFile.new(value, content_type)
               end
-            files.each do |file|
-              merge_param!(params, field['name'].to_s, file)
-            end
+            merge_param!(params, field['name'].to_s, file)
           else
-            path_names.each do |path_name|
-              merge_param!(params, field['name'].to_s, File.basename(path_name))
-            end
+            merge_param!(params, field['name'].to_s, File.basename(field['value'].to_s))
           end
         else
           merge_param!(params, field['name'].to_s, field['value'].to_s)
diff --git a/lib/capybara/rack_test/node.rb b/lib/capybara/rack_test/node.rb
index 9f71334a..10e02dac 100644
--- a/lib/capybara/rack_test/node.rb
+++ b/lib/capybara/rack_test/node.rb
@@ -12,6 +12,9 @@ class Capybara::RackTest::Node < Capybara::Driver::Node
   end
 
   def set(value)
+    if (Array === value) && !self[:multiple]
+      raise ArgumentError.new "Value cannot be an Array when 'multiple' attribute is not present. Not a #{value.class}"
+    end
     if tag_name == 'input' and type == 'radio'
       other_radios_xpath = XPath.generate { |x| x.anywhere(:input)[x.attr(:name).equals(self[:name])] }.to_s
       driver.dom.xpath(other_radios_xpath).each { |node| node.remove_attribute("checked") }
@@ -29,7 +32,17 @@ class Capybara::RackTest::Node < Capybara::Driver::Node
         # Firefox, allowing no input
         value = value[0...self[:maxlength].to_i]
       end
-      native['value'] = value.to_s
+      if Array === value #Assert multiple attribute is present
+        value.each do |v|
+          new_native = native.clone
+          new_native.remove_attribute('value')
+          native.add_next_sibling(new_native)
+          new_native['value'] = v.to_s
+        end
+        native.remove
+      else
+        native['value'] = value.to_s
+      end
     elsif tag_name == "textarea"
       native.content = value.to_s
     end
diff --git a/lib/capybara/selenium/node.rb b/lib/capybara/selenium/node.rb
index f7629deb..c87d2c09 100644
--- a/lib/capybara/selenium/node.rb
+++ b/lib/capybara/selenium/node.rb
@@ -18,12 +18,15 @@ class Capybara::Selenium::Node < Capybara::Driver::Node
   end
 
   def set(value)
+    if (Array === value) && !self[:multiple]
+      raise ArgumentError.new "Value cannot be an Array when 'multiple' attribute is not present. Not a #{value.class}"
+    end
     if tag_name == 'input' and type == 'radio'
       click
     elsif tag_name == 'input' and type == 'checkbox'
       click if value ^ native.attribute('checked').to_s.eql?("true")
     elsif tag_name == 'input' and type == 'file'
-      path_names = value.to_s.empty? ? [] : YAML::load(value.to_s)
+      path_names = value.to_s.empty? ? [] : value
       resynchronize do
         native.send_keys(*path_names)
       end