diff --git a/mozilla/configure.in b/mozilla/configure.in
index 8fdad569123..6f6f4267aed 100644
--- a/mozilla/configure.in
+++ b/mozilla/configure.in
@@ -79,7 +79,7 @@ dnl Set the version number of the libs included with mozilla
 dnl ========================================================
 MOZJPEG=62
 MOZPNG=10009
-MOZMNG="((1<<16)|(0<<8)|(3))"
+MOZMNG="((1<<16)|(0<<8)|(4))"
 NSPR_VERSION=4
 
 dnl Set the minimum version of toolkit libs used by mozilla
diff --git a/mozilla/modules/libimg/mng/libmng_pixels.c b/mozilla/modules/libimg/mng/libmng_pixels.c
index 250acb55058..9c8bc9027b5 100644
--- a/mozilla/modules/libimg/mng/libmng_pixels.c
+++ b/mozilla/modules/libimg/mng/libmng_pixels.c
@@ -935,7 +935,7 @@ mng_retcode display_rgb8_a8 (mng_datap pData)
         for (iX = pData->iSourcel + pData->iCol; iX < pData->iSourcer; iX += pData->iColinc)
         {
           iFGa8 = *(pDataline+3);      /* get alpha values */
-          iBGa8 = *(pScanline+3);
+          iBGa8 = *pAlphaline;
 
           if (iFGa8)                   /* any opacity at all ? */
           {                            /* fully opaque or background fully transparent ? */