SharePoint 2013 Workflow Error: Invalid Text Value

I got the not so obvious error below from a simple SharePoint 2013 style workflow.

Invalid text value.
A text field contains invalid data. Please check the value and try again.

The problem was actually pretty simple. I was trying to write more the 255 characters to the Workflow Log. You will get the same error writing more than 255 characters to a Single Line of Text column. You can use an Extract Substring from Start of String action to retrieve only the first 255 characters.