OleDb parameter replacement broken?

I am having issues with parameter replacements with OleDb. Code is provided below. Hopfully I'm just doing something wrong, but not sure.

Query:

select distinct 
                PLITM as ItemNumber
                from SomeSchema.F564501 
                JOIN SomeSchema.F564541 ON CLY56BKY = PLY56BKY 
                LEFT JOIN SomeSchema.F564540 ON SPITM = PLITM AND CLAN8 = SPAN8  
                WHERE PLUORG = 1 AND CLAN8 = ?RetailerId? AND PLITM IN ?ItemNumbers? 

Code:

IEnumerable<DbModels.Pricing> prices = connection.Query<DbModels.Pricing>(sql, 
                        new
                    {
                        RetailerId = request.RetailerId, //int
                        ItemNumbers = itemNumbers //List<int>, if it helps there are two ints in the list
                    });

Using Mini Profiler the resulting sql and parameters

Parameters:

DECLARE @RetailerId int = 1;

Sql:

select distinct 
                PLITM as ItemNumber
                JOIN SomeSchema.F564541 ON CLY56BKY = PLY56BKY 
                LEFT JOIN SomeSchema.F564540 ON SPITM = PLITM AND CLAN8 = SPAN8  
                WHERE PLUORG = 1 AND CLAN8 = ? AND PLITM IN (?, ?) ;

All that being noted, It will work if i comment out lines 1757 through 1765 in SqlMapper. Let me know if you need anymore info.

Start at SqlMapper lines 1757-1765 and reproduce the reported OleDb query with RetailerId and ItemNumbers. Done means parameter replacement produces valid SQL and binds both values as intended, with the behavior verified against the supplied example.