--- pngvcrd.c.105	Thu Oct 14 05:43:08 1999
+++ pngvcrd.c	Tue Oct 19 08:09:02 1999
@@ -1245,10 +1245,12 @@
                         EMMS
                      }
                   }
-                  else /* if ((pass == 4) || (pass == 5)) */
+                  else if (width) /* && ((pass == 4) || (pass == 5)) */
                   {
                      int width_mmx = ((width >> 1) << 1) - 8;
-                     width -= width_mmx;
+                     if (width_mmx < 0)
+                         width_mmx = 0;
+                     width -= width_mmx;        // 8 or 9 pix, 24 or 27 bytes
                      if (width_mmx)
                      {
                         _asm