diff --git a/lib/capybara/session.rb b/lib/capybara/session.rb
index eeacc069..77d47f7b 100644
--- a/lib/capybara/session.rb
+++ b/lib/capybara/session.rb
@@ -62,6 +62,7 @@ module Capybara
 
     def fill_in(locator, options={})
       msg = "cannot fill in, no text field, text area or password field with id, name, or label '#{locator}' found"
+      raise "Must pass a hash containing 'with'" unless options.kind_of? Hash && !options.index(:with).nil?
       locate(:xpath, XPath.fillable_field(locator), msg).set(options[:with])
     end
 
diff --git a/lib/capybara/spec/session/fill_in_spec.rb b/lib/capybara/spec/session/fill_in_spec.rb
index ddbe6dd3..b1974646 100644
--- a/lib/capybara/spec/session/fill_in_spec.rb
+++ b/lib/capybara/spec/session/fill_in_spec.rb
@@ -82,7 +82,11 @@ shared_examples_for "fill_in" do
       @session.click_button('awesome')
       extract_results(@session)['name'].should == 'Ford Prefect'
     end
-
+    
+    it "should throw an exception if a hash containing 'with' is not provided" do
+      lambda{@session.fill_in 'Name', 'ignu'}.should raise_error
+    end
+    
     context "with ignore_hidden_fields" do
       before { Capybara.ignore_hidden_elements = true }
       after  { Capybara.ignore_hidden_elements = false }