diff --git a/src/libImaging/Convert.c b/src/libImaging/Convert.c
index 5e7479c50..1ad1bdfb8 100644
--- a/src/libImaging/Convert.c
+++ b/src/libImaging/Convert.c
@@ -265,10 +265,10 @@ rgb2l(UINT8 *out, const UINT8 *in, int xsize) {
 static void
 rgb2la(UINT8 *out, const UINT8 *in, int xsize) {
     int x;
-    for (x = 0; x < xsize; x++, in += 4, out += 4) {
+    for (x = 0; x < xsize; x++, in += 4, out += 2) {
         /* ITU-R Recommendation 601-2 (assuming nonlinear RGB) */
-        out[0] = out[1] = out[2] = L24(in) >> 16;
-        out[3] = 255;
+        out[0] = L24(in) >> 16;
+        out[1] = 255;
     }
 }