diff --git a/libswscale/swscale.c b/libswscale/swscale.c
index 76096e7593..e7e81d35cb 100644
--- a/libswscale/swscale.c
+++ b/libswscale/swscale.c
@@ -1665,7 +1665,7 @@ static int packedCopyWrapper(SwsContext *c, const uint8_t* src[], int srcStride[
     uint16_t scale= dither_scale[dst_depth-1][src_depth-1];\
     int shift= src_depth-dst_depth + dither_scale[src_depth-2][dst_depth-1];\
     for (i = 0; i < height; i++) {\
-        uint8_t *dither= dithers[src_depth-9][i&7];\
+        const uint8_t *dither= dithers[src_depth-9][i&7];\
         for (j = 0; j < length-7; j+=8){\
             dst[j+0] = dbswap((bswap(src[j+0]) + dither[0])*scale>>shift);\
             dst[j+1] = dbswap((bswap(src[j+1]) + dither[1])*scale>>shift);\