diff --git a/lib/filter/src/tb_fir_parallel.vhd b/lib/filter/src/tb_fir_parallel.vhd
index 7fda111..2d6ac47 100644
--- a/lib/filter/src/tb_fir_parallel.vhd
+++ b/lib/filter/src/tb_fir_parallel.vhd
@@ -161,7 +161,7 @@ BEGIN
 		
 		while not endfile(fi) loop
 			read(fi, si);
-			x_in <= to_sfixed(to_signed(si, 16));
+			x_in <= to_sfixed(to_signed(si, x_in'length), x_in'left, x_in'right);
 			in_valid <= '1';
 			wait for PERIOD;
 			wait until rising_edge(clk);