Returning Output Parameters with Dapper for .NET Core

I'm struggling with how to properly map output parameters back to an object using Dapper, when I create DynamicParamters from a template object.

var parameters = new DynamicParameters(entity);
parameters.Add("@Id", dbType: DbType.Int32, direction: ParameterDirection.Output);
parameters.Output(entity, x => x.Id);             

await conn.ExecuteAsync(
   "TodoItemInsert", entity, 
    commandType: CommandType.StoredProcedure);  

My hope was that the above code would map the resulting ID back into the entity that I created the parameters from in the first place. No matter what I try I am unable to get the parameter to return from the stored procedure. Calling parameters.Get<int>("@Id") throws a KeyNotFoundException. parameters.Get<int?>("@Id") returns null.

My SQL is a very basic insert sproc

ALTER PROCEDURE [dbo].[TodoItemInsert]
    @Name VARCHAR(255)
    , @Description VARCHAR(512)
    , @DueDate DATETIME = NULL
    , @IsComplete BIT = 0
    , @Id INT OUTPUT 
AS

INSERT INTO
    [TodoItems]
(
    Name
    , Description
    , DueDate
    , IsComplete
)
VALUES
(
    @Name
    , @Description
    , @DueDate
    , @IsComplete
)

SET @Id = SCOPE_IDENTITY()

What is the correct way to get an output parameter back from Dapper when trying to use an object template for my DynamicParameters?