diff --git a/src/art/artJS.tw b/src/art/artJS.tw
index 1b216ebeefdc3075d2fd1bf4347eb1356751f2d7..5d48153998e7eb2774adbf865ff5cef8e5b042da 100644
--- a/src/art/artJS.tw
+++ b/src/art/artJS.tw
@@ -1842,7 +1842,7 @@ window.VectorArt = (function (artSlave) {
 
 	function setButtSize() {
 		/* Size calculations - needs to be done even for amputees */
-		buttSize = Math.clamp(slave.butt, 1, 7) - 1;
+		buttSize = Math.clamp(Math.trunc(slave.butt), 1, 7) - 1;
 	}
 
 	function setHairLength() {