$NetBSD$
png-1.5.1 adjustment, by the time upstream change
probably gone away soon

--- src/image.c.orig	2011-01-16 11:08:48.000000000 +0900
+++ src/image.c	2011-01-16 11:22:27.000000000 +0900
@@ -5538,7 +5538,7 @@
   /* Avoid compiler warning about deprecated direct access to
      png_ptr's fields in libpng versions 1.4.x.  */
   image_error ("PNG error: %s", build_string (msg), Qnil);
-  longjmp (png_ptr->jmpbuf, 1);
+  png_longjmp(png_ptr, 1);
 }
 
 
@@ -5700,7 +5700,7 @@
 
   /* Set error jump-back.  We come back here when the PNG library
      detects an error.  */
-  if (setjmp (png_ptr->jmpbuf))
+  if (png_jmpbuf(png_ptr))
     {
     error:
       if (png_ptr)