http://aur.archlinux.org/packages.php?ID=10325

--- src/rwpng.c
+++ src/rwpng.c
@@ -80,7 +80,7 @@
      * have used slightly more general png_sig_cmp() function instead */
 
     fread(sig, 1, 8, infile);
-    if (!png_check_sig(sig, 8)) {
+    if (png_sig_cmp(sig, 0, 8)) {
         mainprog_ptr->retval = 21;   /* bad signature */
         return mainprog_ptr->retval;
     }