[chef] checksum values in attribute files

[< >]

We're trying to do something pretty simple: Include a checksum value as a
default attribute within a defaults attribute file.

default['foo']['package']['checksum'] =
'c22bb6a227359748618ca1f6fc31b6a05fef3f19dc8251ffb15233b775cd6aff'

But when the associated cookbook is compiled, we encounter the following 
error.

Do you know why this error is occurring?

If we hard code reference to the checksum within the recipe, it works fine.

If we fabricate a hash and include the checksum in it within the attributes
file, it works fine.

[2013-07-22T15:53:35-05:00] INFO: Start handlers complete.
Compiling Cookbooks...

================================================================================
Recipe Compile Error in /.../chef/cookbooks/foo/attributes/default.rb
================================================================================


IndexError
----------
string not matched


Cookbook Trace:
---------------
  /.../chef/cookbooks/foo/attributes/default.rb:6:in `[]='
  /.../chef/cookbooks/foo/attributes/default.rb:6:in `from_file'


Relevant File Content:
----------------------
/.../chef/cookbooks/foo/attributes/default.rb:

  1:  ...
   ...
  6>> default['foo']['package']['checksum'] =
'c22bb6a227359748618ca1f6fc31b6a05fef3f19dc8251ffb15233b775cd6aff'
  7: ...
   ...