diff --git a/bricks/math/HalfAdder.cs b/bricks/math/HalfAdder.cs
index 081f496..24f032b 100644
--- a/bricks/math/HalfAdder.cs
+++ b/bricks/math/HalfAdder.cs
@@ -19,7 +19,7 @@ datablock fxDTSBrickData(LogicGate_HalfAdder_Data)
 	logicUpdate =
 		"return function(gate) " @
 		"	Gate.setportstate(gate, 3, bit.bxor(Gate.getportstate(gate, 1), Gate.getportstate(gate, 2))) " @
-		"	Gate.setportstate(gate, 4, (Gate.getportstate(gate, 1) and Gate.getportstate(gate, 2)) and 1 or 0) " @
+		"	Gate.setportstate(gate, 4, Gate.getportstate(gate, 1)*Gate.getportstate(gate, 2)) " @
 		"end"
 	;