diff --git a/lib/sinatra/base.rb b/lib/sinatra/base.rb
index 7172a174..6562af00 100644
--- a/lib/sinatra/base.rb
+++ b/lib/sinatra/base.rb
@@ -96,6 +96,14 @@ module Sinatra
 
     # Halt processing and redirect to the URI provided.
     def redirect(uri, *args)
+      if not uri =~ /^https?:\/\//
+        # According to RFC 2616 section 14.30, “the field value consists of a single absolute URI”
+        abs_uri = request.scheme + "://"
+        abs_uri << request.host
+        abs_uri << ":#{port}" if request.scheme == "https" and request.port != 443 or request.scheme == "http" and request.port != 80
+        abs_uri << uri
+        uri = abs_uri
+      end
       status 302
       response['Location'] = uri
       halt(*args)
diff --git a/test/filter_test.rb b/test/filter_test.rb
index 4689913c..11a3d8e4 100644
--- a/test/filter_test.rb
+++ b/test/filter_test.rb
@@ -55,7 +55,7 @@ class BeforeFilterTest < Test::Unit::TestCase
 
     get '/foo'
     assert redirect?
-    assert_equal '/bar', response['Location']
+    assert_equal 'http://example.org/bar', response['Location']
     assert_equal '', body
   end
 
@@ -189,7 +189,7 @@ class AfterFilterTest < Test::Unit::TestCase
 
     get '/foo'
     assert redirect?
-    assert_equal '/bar', response['Location']
+    assert_equal 'http://example.org/bar', response['Location']
     assert_equal '', body
   end
 
diff --git a/test/helpers_test.rb b/test/helpers_test.rb
index 647a1dce..3be2a839 100644
--- a/test/helpers_test.rb
+++ b/test/helpers_test.rb
@@ -58,7 +58,7 @@ class HelpersTest < Test::Unit::TestCase
       get '/'
       assert_equal 302, status
       assert_equal '', body
-      assert_equal '/foo', response['Location']
+      assert_equal 'http://example.org/foo', response['Location']
     end
 
     it 'uses the code given when specified' do
@@ -72,7 +72,7 @@ class HelpersTest < Test::Unit::TestCase
       get '/'
       assert_equal 301, status
       assert_equal '', body
-      assert_equal '/foo', response['Location']
+      assert_equal 'http://example.org/foo', response['Location']
     end
 
     it 'redirects back to request.referer when passed back' do
@@ -85,7 +85,7 @@ class HelpersTest < Test::Unit::TestCase
       request = Rack::MockRequest.new(@app)
       response = request.get('/try_redirect', 'HTTP_REFERER' => '/foo')
       assert_equal 302, response.status
-      assert_equal '/foo', response['Location']
+      assert_equal 'http://example.org/foo', response['Location']
     end
   end