diff --git a/lib/rack/utils.rb b/lib/rack/utils.rb
index b39284ff0..a7dc265f5 100644
--- a/lib/rack/utils.rb
+++ b/lib/rack/utils.rb
@@ -319,7 +319,7 @@ def to_hash
       end
 
       def [](k)
-        super(@names[k] ||= @names[k.downcase])
+        super(k) || super(@names[k.downcase])
       end
 
       def []=(k, v)
diff --git a/test/spec_utils.rb b/test/spec_utils.rb
index 929f8e710..82580d138 100644
--- a/test/spec_utils.rb
+++ b/test/spec_utils.rb
@@ -309,6 +309,12 @@
     end
   end
 
+  should "not create headers out of thin air" do
+    h = Rack::Utils::HeaderHash.new
+    h['foo']
+    h['foo'].should.be.nil
+    h.should.not.include 'foo'
+  end
 end
 
 describe Rack::Utils::Context do