how to wrap a C object when field names are Nim keywords?

[Niminem]

C Library struct:
    
    
    typedef struct lxw_conditional_format {
        uint8_t type;
        uint8_t criteria;
        double value;
        lxw_format *format;
    }
    
    
    Run

Nim object:
    
    
    lxw_conditional_format* = ref object
            `type`* :lxw_conditional_format_types
            criteria* :lxw_conditional_criteria
            value* :cdouble
            format* :lxw_formatPtr
    
    # C function below
    # lxw_error worksheet_conditional_format_range(lxw_worksheet *worksheet,
    #                                              lxw_row_t first_row,
    #                                              lxw_col_t first_col,
    #                                              lxw_row_t last_row,
    #                                              lxw_col_t last_col,
    #                                              lxw_conditional_format
    #                                              *conditional_format);
    
    proc conditional_format_range*(worksheet :lxw_worksheetPtr, first_row 
:lxw_row_t, first_col :lxw_col_t, last_row :lxw_row_t, last_col :lxw_col_t, 
conditional_format :ptr lxw_conditional_format) :lxw_error 
{.importc:"worksheet_conditional_format_range",discardable.}
    
    
    Run

The C struct says uint8 for the type and criteria fields, but it takes an enum 
that corresponds to those numbers.

My implementation:
    
    
    var redFmt = workbook.add_format()
    redFmt.set_bg_color(0xFFC7CE)
    redFmt.set_fg_color(0x9C0006)
    
    var redCFmt = lxw_conditional_format()
    redCFmt.kind = LXW_CONDITIONAL_TYPE_CELL
    redCFmt.criteria = LXW_CONDITIONAL_CRITERIA_LESS_THAN
    redCFmt.value = 0
    redCFmt.format = redFmt
    
    echo outputSheet.conditional_format_range(12,16,
            19,18,redCFmt.addr)
    
    
    Run

I get an error called "parameter validation error", also saying "invalid type 
value".