diff --git a/lib/oat/adapters/hal.rb b/lib/oat/adapters/hal.rb
index cafdac0..c8801fb 100644
--- a/lib/oat/adapters/hal.rb
+++ b/lib/oat/adapters/hal.rb
@@ -3,7 +3,7 @@ module Oat
   module Adapters
     class HAL < Oat::Adapter
       def link(rel, opts = {})
-        data[:_links][rel] = opts
+        data[:_links][rel] = opts if opts[:href]
       end
 
       def properties(&block)
diff --git a/spec/adapters/hal_spec.rb b/spec/adapters/hal_spec.rb
index d7e557e..4aa76ca 100644
--- a/spec/adapters/hal_spec.rb
+++ b/spec/adapters/hal_spec.rb
@@ -17,6 +17,8 @@
         h[:controller_name].should == 'some_controller'
         # links
         h[:_links][:self][:href].should == "http://foo.bar.com/#{user.id}"
+        # HAL Spec says href is REQUIRED
+        h[:_links].should_not include(:empty)
         # embedded manager
         h[:_embedded][:manager].tap do |m|
           m[:id].should == manager.id
diff --git a/spec/fixtures.rb b/spec/fixtures.rb
index 7916acd..b3ffe0b 100644
--- a/spec/fixtures.rb
+++ b/spec/fixtures.rb
@@ -12,6 +12,7 @@ def self.included(base)
         schema do
           type 'user'
           link :self, href: url_for(item.id)
+          link :empty, href: nil
 
           property :id, item.id
           map_properties :name, :age