diff --git a/wp-includes/media.php b/wp-includes/media.php
index 7f34963842..f57e8de4ab 100644
--- a/wp-includes/media.php
+++ b/wp-includes/media.php
@@ -351,6 +351,10 @@ function image_resize( $file, $max_w, $max_h, $crop=false, $suffix=null, $dest_p
 	}
 
 	imagecopyresampled( $newimage, $image, $dst_x, $dst_y, $src_x, $src_y, $dst_w, $dst_h, $src_w, $src_h);
+	
+	// convert from full colors to index colors, like original PNG.
+	if ( IMAGETYPE_PNG == $orig_type && !imageistruecolor( $image ) )
+		imagetruecolortopalette( $newimage, false, imagecolorstotal( $image ) );
 
 	// we don't need the original in memory anymore
 	imagedestroy( $image );