Wire error stating FIFO Data type is 1D array

I have a Host to FPGA DMA FIFO with data type defined as U32. On the Host, when I try to wire a U32 constant to the Data field in the Invoke Method block for the FIFO write, I get a wiring error stating that the sink type is a U32 1D array. Why is this happening when a FIFO can't use arrays as a data type?  Attached a screenshot of this error.