ActiveSupport::SafeBuffer::SafeConcatError Ruby on Rails 5.1.2 Class ActiveSupport::SafeBuffer::SafeConcatError < StandardError activesupport/lib/active_support/core_ext/string/output_safety.rb Raised when ActiveSupport::SafeBuffer#safe_concat is called on unsafe buffers. Methods N new Class Public methods new() Link Source: show | on GitHub # File activesupport/lib/active_support/core_ext/string/output_safety.rb, line 147 def initialize super "Could not concatenate to the buffer because it is not html safe." end