I have upgraded from ajv 4.x to ajv 5.0 and I now get above errors when validating json files that I generate using the excellent 'typescript-json-schema' module that generate json schema with
"$schema": "http://json-schema.org/draft-04/schema#".

What version of Ajv are you using? Does the issue happen if you use the latest version?
5.0

Ajv options object

allErrors: true, verbose: false, addUsedSchema: false, inlineRefs: false,

JSON Schema

{
  ...
  "$schema": "http://json-schema.org/draft-04/schema#"
}

Validation result, data AFTER validation, error messages

 Error: no schema with key or ref "http://json-schema.org/draft-04/schema#"

What results did you expect?

The schema to validate like it did in ajv 4.x

Note, as my schemas are autogenerated they are a little difficult to change, so it would be great if Ajv 5 could accept them (like Ajv 4).