diff --git a/actionpack/lib/action_view/base.rb b/actionpack/lib/action_view/base.rb
index 81a8299e91820f97aa875c28b0d03cad82310d91..d73fb643e8e0932f09dc915855b921660e06e051 100644
--- a/actionpack/lib/action_view/base.rb
+++ b/actionpack/lib/action_view/base.rb
@@ -516,8 +516,7 @@ def find_template_extension_from_handler(template_path, formatted = nil)
       
       # Determine the template extension from the <tt>@first_render</tt> filename
       def find_template_extension_from_first_render
-        extension = @first_render.to_s.sub /^\w+\.?/, ''
-        extension.blank? ? nil : extension
+        File.basename(@first_render.to_s)[/^[^.]+\.(.+)$/, 1]
       end
 
       # This method reads a template file.
diff --git a/actionpack/test/action_view_test.rb b/actionpack/test/action_view_test.rb
new file mode 100644
index 0000000000000000000000000000000000000000..729438af320804ab136aa82d3006e09960658ae4
--- /dev/null
+++ b/actionpack/test/action_view_test.rb
@@ -0,0 +1,26 @@
+require File.dirname(__FILE__) + '/abstract_unit'
+require 'test/unit'
+
+class ActionViewTests < Test::Unit::TestCase
+  def test_find_template_extension_from_first_render
+    base = ActionView::Base.new
+
+    assert_nil base.send(:find_template_extension_from_first_render)
+
+    {
+      nil => nil,
+      '' => nil,
+      'foo' => nil,
+      '/foo' => nil,
+      'foo.rb' => 'rb',
+      'foo.bar.rb' => 'bar.rb',
+      'baz/foo.rb' => 'rb',
+      'baz/foo.bar.rb' => 'bar.rb',
+      'baz/foo.o/foo.rb' => 'rb',
+      'baz/foo.o/foo.bar.rb' => 'bar.rb',
+    }.each do |input,expectation|
+      base.instance_variable_set('@first_render', input)
+      assert_equal expectation, base.send(:find_template_extension_from_first_render)
+    end
+  end
+end