SharePoint SP.UserProfiles.PeopleManager GetMyProperties Unknown Error

Problem

When attempting to query SharePoint User Profile using REST at _api/SP.UserProfiles.PeopleManager/GetMyProperties, you get error

<m:error xmlns:m="http://schemas.microsoft.com/ado/2007/08/dataservices/metadata">
<m:code>-1, Microsoft.SharePoint.Client.UnknownError</m:code>
<m:message xml:lang="en-US">Unknown Error</m:message>
</m:error>

Solution

Go to Central Admin –> User Profile Service Application –> Setup My Sites

Fill in the MySite Host Location field. It will also work if you have centralized MySite host located on another farm.

Done!