wbm_sel_o == 0 during read transactions

[epsilon537]

The picorv32_wb state machine always sets wbm_sel_o to 0 during Wishbone read transactions:

				if (mem_valid) begin
					wbm_adr_o <= mem_addr;
					wbm_dat_o <= mem_wdata;
					wbm_we_o <= we;
					wbm_sel_o <= mem_wstrb;

During read transactions mem_wstrb will be 0, so wbm_sel_o gets set to 0. According to the Wishbone spec, sel_o also applies to read transactions, however. Shouldn't wbm_sel_o be set to 4'b1111 during read transactions?