diff --git a/lib/fb_graph2.rb b/lib/fb_graph2.rb
index f5cc9be..f41a679 100644
--- a/lib/fb_graph2.rb
+++ b/lib/fb_graph2.rb
@@ -2,6 +2,7 @@ require 'active_support'
 require 'active_support/core_ext'
 require 'active_support/concern'
 require 'rack/oauth2'
+require 'patch/rack/oauth2/util'
 
 module FbGraph2
   mattr_accessor :root_url, :api_version, :gem_version, :logger, :debugging, :_http_config_, :object_classes
diff --git a/lib/fb_graph2/auth/signed_request.rb b/lib/fb_graph2/auth/signed_request.rb
index e1451b5..8754956 100644
--- a/lib/fb_graph2/auth/signed_request.rb
+++ b/lib/fb_graph2/auth/signed_request.rb
@@ -27,6 +27,7 @@ module FbGraph2
 
       def instantiate(client)
         if payload[:code].present?
+          client.redirect_uri ||= ''
           client.authorization_code = payload[:code]
           self.access_token = client.access_token!
         else
diff --git a/lib/patch/rack/oauth2/util.rb b/lib/patch/rack/oauth2/util.rb
new file mode 100644
index 0000000..4834015
--- /dev/null
+++ b/lib/patch/rack/oauth2/util.rb
@@ -0,0 +1,14 @@
+# NOTE: Authorization code given via FB JS SDK needs blank string as redirect_uri
+module Rack::OAuth2::Util
+  class << self
+    def compact_hash_with_blank_redirect_uri(hash)
+      original_redirect_uri = hash[:redirect_uri]
+      result = compact_hash_without_blank_redirect_uri hash
+      if original_redirect_uri
+        result[:redirect_uri] ||= original_redirect_uri
+      end
+      result
+    end
+    alias_method_chain :compact_hash, :blank_redirect_uri
+  end
+end
\ No newline at end of file