diff --git a/techlibs/gowin/cells_sim.v b/techlibs/gowin/cells_sim.v
index 76635355d95..58a2f52e664 100644
--- a/techlibs/gowin/cells_sim.v
+++ b/techlibs/gowin/cells_sim.v
@@ -1005,7 +1005,7 @@ always @* begin
 			C = I0;
 		end
 		MULT: begin
-			S = I0 & I1;
+			S = (I0 & I1) ^ I3;
 			C = I0 & I1;
 		end
 	endcase