diff --git a/image/color/color.go b/image/color/color.go
index bfd5b39..f57e773 100644
--- a/image/color/color.go
+++ b/image/color/color.go
@@ -22,9 +22,9 @@ func ToRGBA (c color.Color) color.RGBA {
 // Premultiply applies alpha-premultiplication that colors must apply as per
 // color.Color.RGBA. This is an intrinsically lossy proccess.
 func Premultiply (ur, ug, ub, ua uint32) (r, g, b, a uint32) {
-	return (ur * a) / 0xFFFF,
-		(ug * a) / 0xFFFF,
-		(ub * a) / 0xFFFF,
+	return (ur * ua) / 0xFFFF,
+		(ug * ua) / 0xFFFF,
+		(ub * ua) / 0xFFFF,
 		ua
 }