diff --git a/libpng-manual.txt b/libpng-manual.txt
index b787a3d06..896c97a87 100644
--- a/libpng-manual.txt
+++ b/libpng-manual.txt
@@ -4065,10 +4065,11 @@ a 16-bit linear encoded PNG file is written.
 
 With all APIs row_stride is handled as in the read APIs - it is the spacing
 from one row to the next in component sized units (float) and if negative
-indicates a bottom-up row layout in the buffer.
+indicates a bottom-up row layout in the buffer.  If you pass zero, libpng will
+calculate the row_stride for you from the width and number of channels.
 
 Note that the write API does not support interlacing, sub-8-bit pixels,
-and indexed (paletted) images.
+indexed (paletted) images, or most ancillary chunks.
 
 VI. Modifying/Customizing libpng
 
diff --git a/libpng.3 b/libpng.3
index 95a848515..cb32805c7 100644
--- a/libpng.3
+++ b/libpng.3
@@ -4569,10 +4569,11 @@ a 16-bit linear encoded PNG file is written.
 
 With all APIs row_stride is handled as in the read APIs - it is the spacing
 from one row to the next in component sized units (float) and if negative
-indicates a bottom-up row layout in the buffer.
+indicates a bottom-up row layout in the buffer.  If you pass zero, libpng will
+calculate the row_stride for you from the width and number of channels.
 
 Note that the write API does not support interlacing, sub-8-bit pixels,
-and indexed (paletted) images.
+indexed (paletted) images, or most ancillary chunks.
 
 .SH VI. Modifying/Customizing libpng
 
diff --git a/png.h b/png.h
index 9a6b809a9..a3eb41704 100644
--- a/png.h
+++ b/png.h
@@ -3211,9 +3211,11 @@ PNG_EXPORT(240, int, png_image_write_to_stdio, (png_imagep image, FILE *file,
  *
  * With all APIs row_stride is handled as in the read APIs - it is the spacing
  * from one row to the next in component sized units (1 or 2 bytes) and if
- * negative indicates a bottom-up row layout in the buffer.
+ * negative indicates a bottom-up row layout in the buffer.  If row_stride is zero,
+ * libpng will calculate it for you from the image width and number of channels.
  *
- * Note that the write API does not support interlacing or sub-8-bit pixels.
+ * Note that the write API does not support interlacing, sub-8-bit pixels, indexed
+ * PNG (color_type 3) or most ancillary chunks.
  */
 #endif /* STDIO */
 #endif /* SIMPLIFIED_WRITE */