Google analytics event earn_virtual_currency registered with error 19

Question

I am making a game, in Java for Android.

Here is the code:

Bundle bundle = new Bundle();
bundle.putLong(FirebaseAnalytics.Param.VALUE, count);
bundle.putString(FirebaseAnalytics.Param.VIRTUAL_CURRENCY_NAME, "Coins");
bundle.putString(FirebaseAnalytics.Param.LEVEL, level);
analytics.logEvent(FirebaseAnalytics.Event.EARN_VIRTUAL_CURRENCY, bundle);

Here is what I get in the table:

error_value: "currency" firebase_error: 19

Everything worked until recently, but now I can not register this event. Google documentation tells that both parameters VIRTUAL_CURRENCY_NAME and VALUE are optional.

Another event, SPEND_VIRTUAL_CURRENCY, gets registered without any problems.

What's wrong?