diff --git a/src/enc/picture_csp_enc.c b/src/enc/picture_csp_enc.c
index b3510a81..718e014e 100644
--- a/src/enc/picture_csp_enc.c
+++ b/src/enc/picture_csp_enc.c
@@ -29,11 +29,15 @@
 #define USE_INVERSE_ALPHA_TABLE
 
 #ifdef WORDS_BIGENDIAN
-#define ALPHA_OFFSET 0   // uint32_t 0xff000000 is 0xff,00,00,00 in memory
+// uint32_t 0xff000000 is 0xff,00,00,00 in memory
+#define CHANNEL_OFFSET(i) (i)
 #else
-#define ALPHA_OFFSET 3   // uint32_t 0xff000000 is 0x00,00,00,ff in memory
+// uint32_t 0xff000000 is 0x00,00,00,ff in memory
+#define CHANNEL_OFFSET(i) (3-(i))
 #endif
 
+#define ALPHA_OFFSET CHANNEL_OFFSET(0)
+
 //------------------------------------------------------------------------------
 // Detection of non-trivial transparency
 
@@ -997,10 +1001,10 @@ static int PictureARGBToYUVA(WebPPicture* picture, WebPEncCSP colorspace,
     return WebPEncodingSetError(picture, VP8_ENC_ERROR_INVALID_CONFIGURATION);
   } else {
     const uint8_t* const argb = (const uint8_t*)picture->argb;
-    const uint8_t* const a = argb + (0 ^ ALPHA_OFFSET);
-    const uint8_t* const r = argb + (1 ^ ALPHA_OFFSET);
-    const uint8_t* const g = argb + (2 ^ ALPHA_OFFSET);
-    const uint8_t* const b = argb + (3 ^ ALPHA_OFFSET);
+    const uint8_t* const a = argb + CHANNEL_OFFSET(0);
+    const uint8_t* const r = argb + CHANNEL_OFFSET(1);
+    const uint8_t* const g = argb + CHANNEL_OFFSET(2);
+    const uint8_t* const b = argb + CHANNEL_OFFSET(3);
 
     picture->colorspace = WEBP_YUV420;
     return ImportYUVAFromRGBA(r, g, b, a, 4, 4 * picture->argb_stride,