org.springframework.http.converter.HttpMessageNotWritableException: Could not write JSON: java.lang.String cannot be cast to java.lang.Enum

Question

I have a Spring boot application. spring-boot-starter-parent 2.3.0.RELEASE

I'm trying to get a list of objects and expect to get something like this:

{
    "items": [
        {
            "role": "MASTER",
            "module": "USER_EDIT",
            "permissions": [
                 "READ", "WRITE"
            ]
        }
    ],
    "total": 1
}

But I receive an exception:

org.springframework.http.converter.HttpMessageNotWritableException: Could not write JSON: 
java.lang.String cannot be cast to java.lang.Enum; nested exception is com.fasterxml.jackson.databind.JsonMappingException: java.lang.String cannot be cast to java.lang.Enum (through reference chain: com.myproject.dto.ListDto["items"]->java.util.ArrayList[0]->com.myproject.dto.PermissionDto["permissions"]->java.util.ArrayList[0])
...
Caused by: com.fasterxml.jackson.databind.JsonMappingException: java.lang.String cannot be cast to java.lang.Enum (through reference chain: com.myproject.dto.ListDto["items"]->java.util.ArrayList[0]->com.myproject.dto.PermissionDto["permissions"]->java.util.ArrayList[0])
at com.fasterxml.jackson.databind.JsonMappingException.wrapWithPath(JsonMappingException.java:397)
at com.fasterxml.jackson.databind.JsonMappingException.wrapWithPath(JsonMappingException.java:368)
at com.fasterxml.jackson.databind.ser.std.StdSerializer.wrapAndThrow(StdSerializer.java:338)
at com.fasterxml.jackson.databind.ser.impl.IndexedListSerializer.serializeContentsUsing(IndexedListSerializer.java:148)
...
Caused by: java.lang.ClassCastException: java.lang.String cannot be cast to java.lang.Enum
at com.fasterxml.jackson.databind.ser.std.EnumSerializer.serialize(EnumSerializer.java:27)
at com.fasterxml.jackson.databind.ser.impl.IndexedListSerializer.serializeContentsUsing(IndexedListSerializer.java:142)
...

Api method:

@GetMapping
public ListDto<PermissionDto> permissions() {
    return new ListDto<>(permissionsService.list(), permissionsService.count());
}

ListDto:

@Data
@AllArgsConstructor
public class ListDto<T> {
    private List<T> items;
    private long total;
}

PermissionDto:

@Data
public class PermissionDto {
    private Role role;
    private Module module;
    private List<Permission> permissions;
}

Permission:

public enum Permission {
    READ,
    WRITE,
    UPDATE,
    DELETE;
}