diff --git a/src/enc/picture_tools.c b/src/enc/picture_tools.c
index 7c736463..bf97af84 100644
--- a/src/enc/picture_tools.c
+++ b/src/enc/picture_tools.c
@@ -11,6 +11,8 @@
 //
 // Author: Skal (pascal.massimino@gmail.com)
 
+#include <assert.h>
+
 #include "./vp8enci.h"
 #include "../dsp/yuv.h"
 
@@ -120,6 +122,24 @@ void WebPCleanupTransparentArea(WebPPicture* pic) {
 #undef SIZE
 #undef SIZE2
 
+void WebPCleanupTransparentAreaLossless(WebPPicture* const pic) {
+  int x, y, w, h;
+  uint32_t* argb;
+  assert(pic != NULL && pic->use_argb);
+  w = pic->width;
+  h = pic->height;
+  argb = pic->argb;
+
+  for (y = 0; y < h; ++y) {
+    for (x = 0; x < w; ++x) {
+      if ((argb[x] & 0xff000000) == 0) {
+        argb[x] = 0x00000000;
+      }
+    }
+    argb += pic->argb_stride;
+  }
+}
+
 //------------------------------------------------------------------------------
 // Blend color and remove transparency info
 
diff --git a/src/enc/vp8enci.h b/src/enc/vp8enci.h
index 1a7ebe57..08b26ef0 100644
--- a/src/enc/vp8enci.h
+++ b/src/enc/vp8enci.h
@@ -514,6 +514,10 @@ int WebPPictureAllocARGB(WebPPicture* const picture, int width, int height);
 // Returns false in case of error (invalid param, out-of-memory).
 int WebPPictureAllocYUVA(WebPPicture* const picture, int width, int height);
 
+// Clean-up the RGB samples under fully transparent area, to help lossless
+// compressibility (no guarantee, though). Assumes that pic->use_argb is true.
+void WebPCleanupTransparentAreaLossless(WebPPicture* const pic);
+
   // in near_lossless.c
 // Near lossless preprocessing in RGB color-space.
 int VP8ApplyNearLossless(int xsize, int ysize, uint32_t* argb, int quality);
diff --git a/src/enc/webpenc.c b/src/enc/webpenc.c
index b5feb59b..fece7369 100644
--- a/src/enc/webpenc.c
+++ b/src/enc/webpenc.c
@@ -324,14 +324,15 @@ int WebPEncode(const WebPConfig* config, WebPPicture* pic) {
   if (pic->width > WEBP_MAX_DIMENSION || pic->height > WEBP_MAX_DIMENSION)
     return WebPEncodingSetError(pic, VP8_ENC_ERROR_BAD_DIMENSION);
 
-  if (!config->exact) {
-    WebPCleanupTransparentArea(pic);
-  }
-
   if (pic->stats != NULL) memset(pic->stats, 0, sizeof(*pic->stats));
 
   if (!config->lossless) {
     VP8Encoder* enc = NULL;
+
+    if (!config->exact) {
+      WebPCleanupTransparentArea(pic);
+    }
+
     if (pic->use_argb || pic->y == NULL || pic->u == NULL || pic->v == NULL) {
       // Make sure we have YUVA samples.
       if (config->preprocessing & 4) {
@@ -379,6 +380,10 @@ int WebPEncode(const WebPConfig* config, WebPPicture* pic) {
       return 0;
     }
 
+    if (!config->exact) {
+      WebPCleanupTransparentAreaLossless(pic);
+    }
+
     ok = VP8LEncodeImage(config, pic);  // Sets pic->error in case of problem.
   }