diff --git a/doc/webp-lossless-bitstream-spec.txt b/doc/webp-lossless-bitstream-spec.txt
index 9f013724..7c140f49 100644
--- a/doc/webp-lossless-bitstream-spec.txt
+++ b/doc/webp-lossless-bitstream-spec.txt
@@ -23,7 +23,7 @@ Abstract
 
 WebP lossless is an image format for lossless compression of ARGB
 images. The lossless format stores and restores the pixel values
-exactly, including the color values for zero alpha pixels. The
+exactly, including the color values for pixels whose alpha value is 0. The
 format uses subresolution images, recursively embedded into the format
 itself, for storing statistical data about the images, such as the used
 entropy codes, spatial predictors, color space conversion, and color