Using a reference in items of array results in error

When a reference is used in items: of an array, e.g. :

type: object
description: Model for response from call to GET products requiring an array of products to be returned.
title: GetProductResponse
properties:
  Products:
    type: array
    items:
      $ref: Product.yaml

and error is thrown while resolving the references:

$ java -jar openapi-diff-cli-2.1.0-beta.4-all.jar --error --fail-on-incompatible source/specification/openapi.yaml destination/specification/openapi.yaml
Unexpected exception. Reason: Invalid ref: ./common/models/Product.yaml
java.lang.IllegalArgumentException: Invalid ref: ./common/models/Product.yaml
        at org.openapitools.openapidiff.core.utils.RefPointer.getRefName(RefPointer.java:60)
        at org.openapitools.openapidiff.core.utils.RefPointer.resolveRef(RefPointer.java:16)
        at org.openapitools.openapidiff.core.compare.SchemaDiff.computeDiffForReal(SchemaDiff.java:337)
        at org.openapitools.openapidiff.core.model.deferred.DeferredSchemaCache.processSchemaQueue(DeferredSchemaCache.java:86)
        at org.openapitools.openapidiff.core.model.deferred.DeferredSchemaCache.process(DeferredSchemaCache.java:64)
        at org.openapitools.openapidiff.core.compare.OpenApiDiff.compare(OpenApiDiff.java:100)
        at org.openapitools.openapidiff.core.compare.OpenApiDiff.compare(OpenApiDiff.java:64)
        at org.openapitools.openapidiff.core.OpenApiCompare.fromSpecifications(OpenApiCompare.java:102)
        at org.openapitools.openapidiff.core.OpenApiCompare.fromLocations(OpenApiCompare.java:91)
        at org.openapitools.openapidiff.cli.Main.main(Main.java:175)

Files GetProductResponse.yaml and Product.yaml both reside in the same directory.

Attachment contains the source and destination folders, which contain a copy of the same openapi spec.
example.zip

添付された example.zip から始めて CLI コマンドを再現し、その後、特に getRefName と resolveRef を中心に RefPointer.java を読み、trace に記載された SchemaDiff と DeferredSchemaCache の呼び出しパスも確認します。配列項目の兄弟ファイルへの $ref が Invalid ref 例外なしに解決され、比較が完了すれば完了です。