diff --git a/libswscale/swscale.c b/libswscale/swscale.c
index d256f10615..0b12b5e20b 100644
--- a/libswscale/swscale.c
+++ b/libswscale/swscale.c
@@ -2253,7 +2253,7 @@ static int planarCopy(SwsContext *c, const uint8_t* src[], int srcStride[], int
 
                 for (i=0; i<height; i++) {
                     for (j=0; j<length; j++)
-                        ((uint16_t*)dstPtr)[j] = bswap_16(((uint16_t*)srcPtr)[j]);
+                        ((uint16_t*)dstPtr)[j] = bswap_16(((const uint16_t*)srcPtr)[j]);
                     srcPtr+= srcStride[plane];
                     dstPtr+= dstStride[plane];
                 }