diff --git a/src/libImaging/Unpack.c b/src/libImaging/Unpack.c
index eed4914f6..1b8b0a4df 100644
--- a/src/libImaging/Unpack.c
+++ b/src/libImaging/Unpack.c
@@ -415,8 +415,8 @@ unpackL4IR(UINT8 *out, const UINT8 *in, int pixels) {
 static void
 unpackLAL(UINT8 *out, const UINT8 *in, int pixels) {
     int i;
-    UINT8 *in1 = in;
-    UINT8 *in2 = in + pixels;
+    const UINT8 *in1 = in;
+    const UINT8 *in2 = in + pixels;
     /* LA, line interleaved */
     for (i = 0; i < pixels; i++) {
         *out++ = *in1++;