Fails based on yaml type

[inspire22]

My project has been around for awhile, and yaml used to store without the object type prefixing the hash data:

--- 
edge_bg: "979949"
ljust: "0"

i.edge_bg
=> nil

If I update it to this, it works:

--- !map:HashWithIndifferentAccess
edge_bg: "979949"
ljust: "0"

i.edge_bg
=> "979949"

Rails still loads/serializes it just fine in either mode

i.colors
=> {"edge_bg"=>"979949", "ljust"=>"0"}

Any suggestions?