ERB "incompatible character encodings: ISO-8859-1 and UTF-8 (Encoding::CompatibilityError)"

If you get the following error with ERB, Slim, Tilt, Ruby 1.9 or any combination of those:

incompatible character encodings: ISO-8859-1 and UTF-8 (Encoding::CompatibilityError)

try adding this:

Encoding.default_external = Encoding::UTF_8
Encoding.default_internal = Encoding::UTF_8