API schema validation error: Contains an invalid property: tokenUrl

I’m working on the Define tab of an API. Schema selection on Define tab is OpenAPI 3.0. Postman is validating the definition and displays the following error:

Validation error. Contains an invalid property: tokenUrl.

Below is a fragment of the definition. I checked the OpenAPI specification for OAuth Flow Object. Spelling of tokenUrl is correct and it is indeed required. If I remove tokenUrl property, validation succeeds.

Am I missing something here?

    "components": {
        "securitySchemes": {
            "Bearer": {
                "type": "oauth2",
                "flows": {
                    "implicit": {
                        "authorizationUrl": "https://example.org/oauth2/authorize",
                        "tokenUrl": "https://example.org/oauth2/token",
                        "refreshUrl": "https://example.org/oauth2/token",
                        "scopes": {}

System Info:
Postman for Windows v8.0.6
win32 10.0.19042 / x64